Battery pack

ABSTRACT

A battery pack includes a non-aqueous electrolyte secondary battery, a rigid covering member, and a protection circuit board. The secondary battery includes a battery element and a flexible covering member formed of a first laminated film composed of a first heat-bonding layer, a first metal layer, and a first outer covering layer laminated successively. The flexible covering member is sealed along around the battery element while leaving electrode terminals of the positive and negative electrodes extended outside the battery element. The rigid covering member is formed of a second laminated film composed of a second heat-bonding layer, a second metal layer, and a second outer covering layer laminated successively. The flexible covering member and the rigid covering member are bonded with an adhesive strength equal to or higher than atmospheric pressure and with a peel strength equal to or lower than a breaking strength of the flexible covering member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese patent ApplicationNo. 2007-104607 filed in the Japanese Patent Office on Apr. 12, 2007,the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present application relates to a battery pack, more particularly, toa battery pack applied to a non-aqueous electrolyte secondary battery,such as a lithium-ion secondary battery.

In recent years, various types of portable electronic devices, such asvideotape recorders (VTRs) with camera, cell phones, and laptopcomputers, are widely used, and those having smaller size and weight arebeing developed. As the portable electronic devices are miniaturized,demand for battery as a power source of them is rapidly increasing. Toreduce the size and weight of the device, the battery design in whichthe battery is lightweight and thin, and the housing space for thedevice can be efficiently used, is desired as well. It is known that, asa battery for meeting the demands, a lithium-ion secondary batteryhaving a large energy density and a large power density is the mostpreferred.

In the development of the lithium-ion secondary battery, putting intopractical use batteries having high selectivity of shape, sheet-typebatteries having a reduced thickness and a large area, or card-typebatteries having a reduced thickness and a small area is desired.

For meeting the demands, it has been recently reported that the thinbattery as described above can be obtained using a casing member in afilm form, such as an aluminum laminated film (see, for example,

TAKAMI Norio, “Ultrathin lithium-ion battery using aluminum laminatedfilm case”, Toshiba Review, Toshiba Corporation, Vol. 56, No. 2,February, 2001, pp. 10-13 (hereinafter referred to as “non-patentdocument 1”)).

FIGS. 1A-1C show the external views of a battery 1 disclosed in thenon-patent document 1. FIGS. 1A, 1B, and 1C are a plan view, a frontview, and a section view of the thin lithium-ion battery for cellularphones, respectively.

The thin battery 1 is produced by covering a flat-type battery element,which is formed of stacking a positive electrode and a negativeelectrode through a separator and spirally winding them, with analuminum laminated film and sealing the film around the battery element.

A positive electrode terminal 2 a and a negative electrode terminal 2 brespectively connected to the positive electrode and negative electrodeare extended outside the battery, for example, from one side of the thinbattery 1, and the aluminum laminated film around the battery elementexcept for one side is sealed and then an electrolyte solution isinjected from the unsealed opening, and finally the side of the filmfrom which the positive electrode terminal 2 a and negative electrodeterminal 2 b are extended is sealed, thus obtaining the thin battery.

This thin battery uses a casing of an aluminum laminated film having athickness of about 100 μm, and hence has small strength, as compared toa battery using a metallic can, and it is difficult to use this batteryas a battery pack as it is. Accordingly, a battery pack containing abattery element covered with a laminated film in a pack housing formedof a plastic and firmly fixed with an adhesive double-faced tape or thelike is widely used. Further, it has been known that the battery packcan be improved in resistance to drop impact or shock by increasing thethickness of the housing.

However, in such a known thin battery, the housing is bonded with thesurface of the battery at limited bonding portions, and hence, when thebattery is dropped from a certain height or higher, there is apossibility that, although the battery element is not damaged, a load isconcentrated on the flexible battery casing to break the casing or apinhole is formed in the metal layer of the casing, and then moistureenters the inside of the battery by passing through the resin layer.

In this case, even in the battery pack which seems to suffer nodeformation or the like from the external view of the pack and which canbe fitted into an electric device, when the casing for battery isbroken, moisture in air reacts with the electrode or electrolyte tocontinuously generate harmful gas, or when only pinhole is formed, themoisture vigorously reacts with the electrode or electrolyte to generategas during the charging, so that the battery pack unusually expands,whereby causing a possibility of breaking the portable electric device.

Further, the pack housing inevitably has a thickness as large as about300 μm or more due to the limitation of the technique for thin plasticmolding or for securing the strength of housing, and therefore it isdifficult to increase the battery volume to be contained in the housing.

SUMMARY

Accordingly, it is desirable to provide a battery pack in which the loadconcentration on the flexible covering member is reduced and hence thebattery pack is improved in reliability or safety after suffering dropand has such strength that the battery pack can resist deformation orthe like when it suffers an impact/shock of short drop. Furthermore, ifthe battery pack suffers an impact/shock such that the flexible coveringmember is damaged, the external view of the resultant battery packadvantageously reveals that the battery pack cannot be subsequentlyfitted into an electric device or charged, the battery pack has suchexcellent volume efficiency that the volume of the battery element to becontained can be as large as possible.

The present inventors have conducted studies with a view towardachieving the above issue. As a result, it has been found that, byappropriately controlling the state of bonding between the flexiblecovering member and the rigid covering member so that the adhesivestrength and peel strength are in the respective predetermined ranges,the issue can be achieved.

In accordance with an embodiment, there is provided a battery pack whichincludes a non-aqueous electrolyte secondary battery, a rigid coveringmember, a protection circuit board. The non-aqueous electrolytesecondary battery includes (a) a battery element including a positiveelectrode, a negative electrode, and a separator which are spirallywound or stacked, the separator being disposed between the positiveelectrode and the negative electrode, the battery element including anon-aqueous electrolyte composition, (b) a flexible covering member,formed of a first laminated film, which covers the batter element. Thefirst laminated film is composed of a first heat-bonding layer, a firstmetal layer, and a first outer covering layer which are laminatedsuccessively. The flexible covering member is sealed along around thebattery element while leaving electrode terminals of the positive andnegative electrodes extended outside the battery element. The rigidcovering member covers the non-aqueous electrolyte secondary batterytogether with the flexible covering member, and is formed of a secondlaminated film composed of a second-heat-bonding layer, a second metallayer, and a second outer covering layer which are laminatedsuccessively. The protection circuit board, housed in the rigid coveringmember, controls a voltage and a current of the non-aqueous electrolytesecondary batter. The battery element and the flexible covering memberadhere to each other. The flexible covering member and the rigidcovering member are bonded with an adhere strength equal to or higherthan atmospheric pressure and with a peel strength equal to or lowerthan a breaking strength of the flexible covering member.

In accordance with another embodiment, there is provided a battery packwhich includes a non-aqueous electrolyte secondary battery and aprotection circuit board. The non-aqueous electrolyte secondary batteryincludes (a) a battery element including a positive electrode, anegative electrode, and a separator which are spirally wound or stacked,the separator being disposed between the positive electrode and thenegative electrode, the battery element including a non-aqueouselectrolyte composition, (b) a flexible covering member, formed of afirst laminated film, which covers a principal portion of the batteryelement, the first laminated film being composed of a first heat-bondinglayer, a first metal layer, and a first outer covering layer which arelaminated successively, (c) a rigid covering member, formed of a secondlaminated film, which covers a remaining portion of the battery elementand the flexible covering member, the second laminated film beingcomposed of a second heat-bonding layer, a second metal layer, and asecond outer covering layer which are laminated successively. Theflexible covering member and the rigid covering member are bonded alongaround the battery element to seal the battery element while leavingelectrode terminals of the positive and negative electrodes extendedoutside the battery element. The protection circuit board, housed in therigid covering member, controls a voltage and a current of thenon-aqueous electrolyte secondary battery. The battery element and theflexible covering member adhere to each other. The flexible coveringmember and the rigid covering member other than around the batteryelement are bonded with an adhesive strength equal to or higher thanatmospheric pressure and with a peel strength equal to or higher than abreaking strength of the flexible covering member.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A to 1C are diagrammatic views showing the structure of thebattery described in the non-patent document 1.

FIG. 2 is a perspective view of a battery pack according to oneembodiment.

FIGS. 3A to 3C are top views showing the structure of a battery packaccording to one embodiment.

FIG. 4 is a perspective view showing the structure of a battery elementin a battery pack according to one embodiment.

FIG. 5 is a perspective view showing the structure of a battery in abattery pack according to one embodiment.

FIG. 6 is a cross-sectional view showing the structure of a flexiblelaminated film in a battery pack according to one embodiment.

FIG. 7 is an exploded perspective view showing the structure of abattery in a battery pack according to one embodiment.

FIGS. 8A and 8B are perspective views showing the structure of a batteryin a battery pack according to one embodiment.

FIG. 9 is a cross-sectional view showing the structure of a rigidlaminated film in a battery pack according to one embodiment.

FIGS. 10A and 10B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIGS. 11A and 11B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIGS. 12A and 12B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIGS. 13A and 13B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIGS. 14A and 14B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIGS. 15A and 15B are perspective and cross-sectional views showing thestructure of a battery assembly in a battery pack according to oneembodiment.

FIG. 16 is a cross-sectional view showing another example of thestructure of a rigid laminated film.

FIG. 17 is a cross-sectional view showing another example of thestructure of a rigid laminated film.

FIG. 18 is a cross-sectional view showing the structure of a rigidlaminated film in a battery pack according to another embodiment.

FIGS. 19A to 19C are top and side views showing a battery pack accordingto another embodiment.

FIGS. 20A and 20B are cross-sectional views showing a battery packaccording to another embodiment.

FIGS. 21A and 21B are cross-sectional views showing a battery packaccording to still another embodiment, which is being produced.

FIGS. 22A and 22B are cross-sectional views showing a battery packaccording to still further another embodiment, which is being produced.

DETAILED DESCRIPTION

The battery pack an embodiment will be described in detail below withreference to the accompanying drawings. In the present specification,with respect to the concentration, content, amount, and others, “%” isgiven by weight unless otherwise specified.

First Embodiment

In the present embodiment, a casing member in which a rigid laminatedfilm having a four-layer structure is used is described.

FIG. 2 shows the external view of a battery pack for lithium-ion polymersecondary battery, which is a battery pack according to one embodiment.The battery pack 40 has a lithium-ion polymer battery, which is anexample of a non-aqueous electrolyte secondary battery, contained in arigid laminated film 41 as a rigid covering member, and a top cover 42and a rear cover 43 which are resin molded covers fitted to openings atthe both ends of the battery pack, and optionally has a product label46.

In the first embodiment and the second embodiment described later,“battery” refers to a battery element covered with a flexible laminatedfilm which is a flexible covering member, “battery assembly” refers to abattery covered with the rigid laminated film 41, and “battery pack”refers to one having the structure shown in FIG. 2, obtained byconnecting a circuit board to the battery assembly and fitting theretothe top cover 42 and rear cover 43.

FIGS. 3A to 3C show the structure of the battery pack 40. The batterypack 40 includes a battery 50 including a battery element covered with aflexible laminated film, a circuit board 44, a top cover 42, and a rearcover 43, wherein the batter 50 is covered with a rigid laminated film41.

The top cover 42 is a resin molded cover which is provided at a topportion from which a positive electrode and a negative electrode areextended, and which is fitted to the opening of the battery assembly.The rear cover 43 is a resin molded cover which is provided at a bottomportion of the battery and fitted to the opening of the battery assembly45.

The top cover 42 and rear cover 43 are fitted to the respective openingsof the battery assembly 45 and then bonded with the battery assembly 45by heat sealing or the like. The top cover 42 is formed of an upperholder 42 a and a lower holder 42 b fitted to each other, and thecircuit board 44 is disposed between the upper holder 42 a and the lowerholder 42 b.

The circuit board 44 has a protection circuit mounted in advancethereon, and the protection circuit is connected by resistance welding,ultrasonic welding, or the like to the positive electrode terminal andnegative electrode terminal extended from the battery 50. The protectioncircuit has a temperature protection element such as a positivetemperature coefficient (PTC) element or a thermistor so as to cut offthe current circuit in the battery if the battery becomeshigh-temperature.

The battery pack 40 includes a terminal for connection with an electricdevice (not shown). The top cover 42 is provided with a terminal windowthrough which the terminal for connection with the electric device isexposed.

Next, the battery element is described.

FIG. 4 shows the structure of a battery element 59 used in the batteryassembly 45.

The battery element 59 includes a strip positive electrode 51, aseparator 53 a, a strip negative electrode 52 disposed opposite thepositive electrode 51, and a separator 53 b, which are stackedsuccessively and spirally wound together in the longitudinal direction,and a gel electrolyte (not shown) is applied to both sides of thepositive electrode 51 and negative electrode 52.

A positive electrode terminal 55 a connected to the positive electrode51 and a negative electrode terminal 55 b connected to the negativeelectrode 52 are extended from the battery element 59, and both sides ofeach of the positive electrode terminal 55 a and the negative electrodeterminal 55 b are covered with resin pieces 56 a and 56 b, respectively,to improve the bonding properties with the laminated film for covering.When an electrolyte solution is used, an electrolyte solution injectionstep is subsequently provided.

Materials constituting the battery element 59 are described below indetail.

Positive Electrode

The positive electrode 51 includes a cathode active material layer 51 aincluding a cathode active material and being formed on both sides of acathode current collector 51 b. The cathode current collector 51 b iscomposed of a metallic foil, such as an aluminum (Al) foil.

The cathode active material layer 51 a includes, for example, a cathodeactive material, a conductor, and a binder. These components areintimately mixed with one another to prepare a positive electrodecomposition, and the positive electrode composition is dispersed in asolvent to form a slurry. Then, the slurry is uniformly applied to thecathode current collector 51 b by a doctor blade method or the like, anddried at a high temperature so that the solvent is volatized to form acathode active material layer.

With respect to the amounts of the cathode active material, conductor,binder, and solvent, there is no particular limitation as long as theyare uniformly dispersed.

As the cathode active material, a composite oxide of lithium and atransition metal, representatively, LiXMO₂ wherein M represents at leastone transition metal, and x varies depending on the charged ordischarged state of the battery, and is generally 0.05 to 1.10 is used.As a transition metal constituting the lithium composite oxide, cobalt(Co), Ni, manganese (Mn), or the like is used.

Specific examples of the lithium composite oxides include LiCoO₂,LiNiO₂, LiMn₂O₄, and LiNi_(y)CO_(1-y)O₂ (0<y<1).

A solid solution obtained by replacing part of the transition metalelement in the lithium composite oxide by another element may be used.Examples of the solid solutions include LiNi_(0.5)CO_(0.5)O₂ andLiNi_(0.8)CO_(0.2)O₂. These lithium composite oxides can generate highvoltage and have excellent energy density. Alternatively, as the cathodeactive material, a metal sulfide or oxide containing no lithium, such asTiS₂, MoS₂, NbSe₂, or V₂O₅, may be used.

As a conductor, a carbon material, such as carbon black or graphite, isused. As a binder, for example, polyvinylinde di-fluoride, orpolytetrafluoroethylene is used. As a solvent, for example,N-methylpyrrolidone is used.

The positive electrode 51 has a positive electrode terminal 55 aconnected to one end of the current collector by spot welding orultrasonic welding. The positive electrode terminal 55 a is desirablycomposed of a metallic foil or mesh, but the terminal may be composed ofa material other than a metal as long as the material iselectrochemically and chemically stable and can achieve electricalconduction.

An example of a material for the positive electrode terminal 55 a is Al.

Negative Electrode

The negative electrode 52 includes an anode active material layer 52 aincluding an anode active material and being formed on both sides of ananode current collector 52 b. The anode current collector 52 b iscomposed of a metallic foil, such as a copper (Cu) foil, a Ni foil, or astainless steel foil.

The anode active material layer 52 a includes, for example, an anodeactive material, and optionally a conductor and a binder. Thesecomponents are intimately mixed with one another to prepare a negativeelectrode composition, and the negative electrode composition isdispersed in a solvent to form a slurry. Then, the slurry is uniformlyapplied to the anode current collector 52 b by a doctor blade method orthe like, and dried at a high temperature so that the solvent isvaporized to form an anode active material layer 52 a. With respect tothe amounts of the anode active material, conductor, binder, andsolvent, there is no particular limitation as long as they are uniformlydispersed.

As the anode active material, lithium metal, a lithium alloy, a carbonmaterial capable of being doped with lithium and dedoped, or a compositematerial of a metal material and a carbon material is used.

Specific examples of carbon materials capable of being doped withlithium and dedoped include graphite, hardly graphitizable carbon, andeasily graphitizable carbon. More specifically, a carbon material, suchas pyrolytic carbon, coke (pitch coke, needle coke, or petroleum coke),graphite, glassy carbon, a calcined product of an organic polymercompound (obtained by carbonizing a phenolic resin, a furan resin, orthe like by calcination at an appropriate temperature), carbon fiber, oractivated carbon, can be used. Further, as a material capable of beingdoped with lithium and dedoped, a polymer, such as polyacetylene orpolypyrrole, or an oxide, such as SnO₂, may be used.

As a material capable of being alloyed with lithium, various types ofmetals may be used, but tin (Sn), cobalt (Co), indium (In), Al, silicon(Si), or an alloy thereof is generally used. When using metalliclithium, it is not always necessary to mix lithium powder with a binderto form a coating film, and a rolled Li metallic sheet may be used.

As a binder, for example, polyvinylidene fluoride or a styrene-butadienerubber is used. As a solvent, for example, N-methylpyrrolidone or methylethyl ketone is used.

Like the positive electrode 51, the negative electrode 52 has a negativeelectrode terminal 55 b connected to one end of the anode currentcollector 52 b by spot welding or ultrasonic welding. The negativeelectrode terminal 52 b is desirably composed of a metallic foil ormesh, but the terminal may be composed of a material other than a metalas long as the material is electrochemically and chemically stable andcan achieve electrical conduction. An example of materials for thenegative electrode terminal 52 b is copper and Ni.

It is preferred that the positive electrode terminal 55 a and thenegative electrode terminal 55 b are extended from the same side, butthey may be extended from any sides as long as short-circuiting or thelike does not occur and there is no adverse effect on the batteryperformance. With respect to the connecting portion between the positiveelectrode terminal 55 a and negative electrode terminal 55 b, theconnecting position and the method for connecting are not limited to theexamples described above as long as electrical contact can be made.

Electrolyte

In the electrolyte, i.e., non-aqueous electrolyte composition, anelectrolyte salt and a non-aqueous solvent generally used in lithium-ionbattery may be used.

Specific examples of non-aqueous solvents include ethylene carbonate(EC), propylene carbonate (PC), γ-butyrolactone, dimethyl carbonate,diethyl carbonate, ethylmethyl carbonate, dipropyl carbonate,ethylpropyl carbonate, and solvents obtained by replacing the hydrogenin the above carbonates by a halogen.

These solvents may be used individually or in combination.

As the electrolyte salt, one which is soluble in the above non-aqueoussolvent is used, and it includes a combination of a cation and an anion.As a cation, an alkali metal or alkaline earth metal is used. As ananion, Cl⁻, Br⁻, I⁻, SCN⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, CF₃SO₃ ⁻, or the likeis used.

Specific examples of electrolyte salts include LiPF₆, LiBF₄,LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, and LiClO₄. With respect to the electrolytesalt concentration, there is no particular limitation as long as theelectrolyte salt can be dissolved in the above solvent, but it ispreferred that the lithium ion concentration is in the range of from 0.4to 2.0 mol/kg, with respect to the non-aqueous solvent.

When using a gel electrolyte, a gel electrolyte is obtained by gellingan electrolyte solution mixture of a nonaqueous electrolyte solvent andan electrolyte salt by a matrix polymer.

As the matrix polymer, there can be used any polymer which is compatiblewith a nonaqueous electrolyte solution including an electrolyte saltdissolved in a non-aqueous solvent and which can gel the electrolytesolution.

Examples of the matrix polymers include polymers comprisingpolyvinylidene fluoride, polyethylene oxide, polypropylene oxide,polyacrylonitrile, or polymethacrylonitrile in repeating units. Thesepolymers may be used individually or in combination.

Separator

The separator is formed of a porous film made of a polyolefin material,such as polypropylene (PP) or polyethylene (PE), or a porous film madeof an inorganic material, such as ceramic nonwoven fabric, and may becomposed of two or more porous films into a laminated structure. Ofthese, a polyethylene or polypropylene porous film may be moreeffective.

Generally, the usable separator preferably has a thickness of 5 to 50μm, more preferably 7 to 30 μm. If the separator thickness is too large,the ratio of the active material to the separator is reduced to lowerthe battery capacity, and further the ion conduction properties becomepoor, so that the current properties become poor. On the other hand, ifthe separator thickness is too small, the film of separator is reducedin mechanical strength.

Fabrication of Battery

The gel electrolyte solution prepared as described above is uniformlyapplied to the positive electrode 51 and negative electrode 52 so thatthe cathode active material layer 51 a and anode active material layer52 a are impregnated with the electrolyte solution, and then kept atroom temperature or subjected to drying process to form gel electrolytelayers. Then, the positive electrode 51, the separator 53 a, thenegative electrode 52, and the separator 53 b are stacked successivelyin this order and spirally wound together to form a battery element 59by using the positive electrode 51 and negative electrode 52 each havinga gel electrolyte layer formed thereon.

Then, the battery element 59 is covered with a flexible laminated film57 and the laminated film is shaped to form a battery 50 shown in FIG.5.

As the flexible laminated film 57, a laminated film having the structureshown in FIG. 6 is used. The flexible laminated film 57 is composed of amultilayer film having a moisture resistance and insulation properties,and including a metallic foil designated by reference numeral 61sandwiched between an outer covering layer 62 composed of a resin filmand a heat-bonding layer (hereinafter, frequently referred to as“sealant layer”) 63 composed of a resin film.

With respect to the thickness of each of the outer covering layer 62,the metallic foil 61, and the sealant layer 63, there is no particularlimitation, but the thicknesses of the outer covering layer, metallicfoil, and sealant layer are respectively about 15 μm, about 35 μm, andabout 30 μm.

The metallic foil 61 improves the casing member in strength, and furtherhas the main role in preventing moisture, oxygen, or light from goinginto the battery to protect the contents, and stainless steel, ironplated with nickel, or the like is appropriately selected and used as amaterial for the metallic foil. From the viewpoint of reduced weight,excellent stretchability, low cost, and excellent workability, aluminum(Al) is more preferred, and the used of aluminum such as 8021O or 8079Omay be preferred.

The metallic foil 61 and the outer covering layer 62, and the metallicfoil 61 and the sealant layer 63 are individually bonded through bondingagent layers 64 and 65, respectively.

When the outer covering layer 62 or sealant layer 63 has heat bondingproperties with the metal or an under coat layer which can beheat-bonded with the outer covering layer 62 or sealant layer 63 isformed on the surface of the metal, the bonding agent layer 64 can beomitted.

In the outer covering layer 62, for achieving good appearance,toughness, heat resistance, flexibility, and the like, polyolefin,polyamide, polyimide, or polyester, specifically, nylon (Ny),polyethylene terephthalate (PET), polyethylene (PE), or polyethylenenaphthalate (PEN) is used, and these materials may be used incombination.

The sealant layer 63 is a portion to be fused due to heat or ultrasonicwaves, and polyethylene (PE), cast polyethylene (CPE), castpolypropylene (CPP), polyethylene terephthalate (PET), nylon (Ny),low-density polyethylene (LDPE), high-density polyethylene (HDPE), orlinear low-density polyethylene (LLDPE) may be used, and these materialsmay be used in combination.

General constituents of the laminated film are as follows: outercovering layer/metallic foil/sealant layer=Ny/Al/CPP. Instead of thiscombination, another combination shown below of general constituents ofthe laminated film may be used.

Specifically, outer covering layer/metallic foil/sealant layer=Ny/Al/PE,PET/Al/CPP, PET/Al/PET/CPP. PET/Ny/Al/CPP, PET/Ny/Al/Ny/CPP,PET/Ny/Al/Ny/PE, Ny/PE/Al/LLDPE, PET/PE/Al/PET/LDPE, orPET/Ny/Al/LDPE/CPP. As the metallic foil, a metal other than Al may beused.

As shown in FIG. 7, a recessed portion 57 a is formed in the flexiblelaminated film 57 by deep-drawing, and the battery element 59 is housedin the recessed portion 57 a, and then the opening of the recessedportion 57 a is covered with the flexible laminated film 57.

Next, three sides of the flexible laminated film around the batteryelement 59 are heat-sealed under a reduced pressure to form a battery50. In the heat sealing under a reduced pressure, the battery element 59adheres to the flexible laminated film 57.

In a battery using an electrolyte solution, an electrolyte solution isinjected at this time. Two sides of the flexible laminated film aroundthe battery element are first heat-sealed, and then an electrolytesolution in a predetermined amount is injected through the remainingopening side, and finally the opening is heat-sealed to obtain abattery.

In the battery 50, considering the subsequent steps in the production,unnecessary portions of the top portion may be removed by trimming. Asshown in FIGS. 8A and 8B, by trimming along the dotted lines designatedby reference character P, for example, interference between the topcover and the flexible laminated film can be reduced.

Fabrication of Battery Assembly

The above-prepared battery is covered with a rigid laminated film toform a battery assembly. First, the structure of the rigid laminatedfilm is described.

As shown in FIG. 9, the rigid laminated film 41 is composed of amultilayer film having a moisture resistance and insulation properties,including a metallic foil designated by reference numeral 71 sandwichedbetween an outer covering layer 72 composed of a resin film and asealant layer 73 composed of a resin film, and having a bonding layer 74under the sealant layer 73. In the present embodiment, the sealant layer73 and bonding layer 74 together form a heat-bonding layer 79 (compositebonding layer) having heat bonding properties with nylon or the like.

In the rigid laminated film 41, with respect to the thickness of each ofthe outer covering layer 72, the metallic foil 71, and the heat-bondinglayer (sealant layer 73+bonding layer 74), there is no particularlimitation, but the thicknesses are respectively 115 μm or less, 330 μmor less, about 25 to 50 μm (sealant layer), and about 1 to 5 μm (bondinglayer).

For securing strength, a rigid (hard) material is used, and the reasonthat the thickness of the outer covering layer 72 is 115 μm or less andthe thickness of the metallic foil 71 is 330 μm or less resides in thatthe increase of the resistance of thermal conduction is prevented.

In the metallic foil 71, a hard metal material is used, and aluminum,stainless steel, copper, titanium, tinplate, galvanized steel, ironplated with nickel, or the like is appropriately selected and used as amaterial. Of these, aluminum (Al) or stainless steel (SUS) ispreferable, and the used of aluminum such as 3003-H18, 3004-H18, andIN30-H18, or stainless steel such as SUS304 and SUS430, is especiallypreferable.

In the outer covering layer 72, for achieving good appearance,toughness, heat resistance, flexibility, and the like, nylon (Ny),polyethylene terephthalate (PET), or polyethylene naphthalate (PEN) isused, and these materials may be used in combination.

The sealant layer 73 is a portion to be fused due to heat or ultrasonicwaves, and polyethylene (PE), cast polypropylene (CPP), polyethyleneterephthalate (PET), nylon (Ny), low-density polyethylene (LDPE),high-density polyethylene (HDPE), or linear low-density polyethylene(LLDPE) may be used, and these materials may be used in combination.

The metallic foil 71 and the outer covering layer 72, and the metallicfoil 71 and the sealant layer 73 are individually bonded through bondingagent layers 75 and 76, respectively.

The heat-bonding layer 74 bonds the battery 50 covered with the flexiblelaminated film 57 with the rigid laminated film 41 without using aseparate bonding member.

Regarding the heat-bonding layer 74, a resin material having excellentbonding properties with Ny, PET, PEN, or the like used in the outercovering layer of the flexible laminated film 57 and having a meltingtemperature which does not adversely affect the battery element is used.Further, the resin material used in the heat-bonding layer 74 has amelting temperature lower than that of the material used in the sealantlayer 73.

Specifically, an ethylene-vinyl acetate copolymer (EVA), anethylene-acrylic acid copolymer, an ethyl acrylate copolymer, a methylacrylate copolymer, a methacrylic acid copolymer, a methyl methacrylatecopolymer, polyacrylonitrile, an ethylene-vinyl alcohol resin, apolyamide resin, a polyester resin, acid-modified polypropylene, or anionomer may be used, and these materials may be used in combination.These materials may be used as a hot-melt adhesive or film or aweathering-resistant adhesive.

The sealant layer 73 serves as a sealing layer in the subsequent heatsealing of the top cover 42 and rear cover 43. Accordingly, a resinmaterial having excellent bonding properties with the top cover 42 andrear cover 43 is selected. In addition, the sealant layer exhibits acushioning effect in bonding the rigid laminated film 41 with thebattery 50.

Specifically, in heat sealing the flexible laminated film 57 as a casingmember for the battery 50 with the rigid laminated film 41 through theheat-bonding layer 74, there is a possibility that they are notsatisfactorily bonded together due to the finely uneven surfaces of theindividual laminated films. When the sealant layer 73 having a thicknessof about 25 to 50 μm is formed, the sealant layer 73 exhibits acushioning effect, so that the laminated films having finely unevensurfaces can be well bonded together.

The bonding state between the flexible covering member and the rigidcovering member, which is the characteristic feature of embodimentsresides is described.

As described above, in the battery pack of embodiments, the flexiblecovering member and the rigid covering member are bonded with anadhesive strength equal to or higher than atmospheric pressure and witha peel strength equal to or lower than a breaking strength of theflexible covering member.

If the adhesive strength is lower than atmospheric pressure, thefollowing disadvantage is caused. When peel stresses are exerted on theportion between the rigid laminated film as a rigid covering member andthe battery body due to a certain factor, the rigid laminated film iseasily peeled, and cannot solely resist buckling stresses in drop or thelike and hence is likely to suffer buckling or the like. Specifically,the adhesive strength is preferably 0.1 MPa or more, more preferably 0.1to 0.5 MPa, further preferably 0.2 to 0.4 MPa.

If the peel strength is higher than a breaking strength of the flexiblecovering member, the following disadvantage is caused. When the rigidlaminated film as a rigid covering member is peeled by a certain factor,the flexible laminated film as a flexible covering member is stretchedand broken, or the flexible laminated film is not broken, but a crack orpinhole is caused in the metal layer. Specifically, the peel strength ispreferably 5 N/mm or less, more preferably 1 to 5 N/mm, furtherpreferably 2 to 4 N/mm.

For achieving the adhesive strength and peel strength in the aboverespective ranges, for example, the flexible covering member and therigid covering member are bonded so that the outer covering layer of theflexible covering member is not melted and the bonding layer of therigid covering member is melted. Specifically, the flexible laminatedfilm 57 and the rigid laminated film 41 are bonded together, but theouter covering layer 62 of the flexible laminated film 57 is not meltedand the heat-bonding layer 79 (sealant layer 73+bonding layer 74) of therigid laminated film 41 is melted.

The state of bonding is not limited to this as long as the adhesivestrength and peel strength are in the above respective ranges.

By providing the bonding state showing the ranges of the adhesivestrength and peel strength, the battery pack has the followingadvantages. The battery pack has strength such that, if the battery packsuffers shock or impact/shock of drop or the like and excess peelstresses are exerted on the portion between the rigid laminated film 57and the flexible laminated film 41, the flexible laminated film 41 isstretched and the rigid laminated film 57 is removed before a pinhole orbreakage is caused. Further, if small stresses are exerted on thelaminated films, the rigid laminated film 57 is unified with the batteryelement due to atmospheric pressure and stretch strength of the flexiblelaminated film 41, so that the battery pack can resist deformation.

As a result, the battery pack of embodiments has appropriate strength.Specifically, when the battery pack suffers an impact/shock of drop suchthat the flexible covering member is not damaged, no defect is caused inthe external view of the pack, which indicates that the battery pack canbe subsequently used. Further, when the battery pack suffers animpact/shock of drop such that the flexible covering member is damaged,the rigid casing is first peeled or removed, which indicates that thebattery pack cannot be used any more. Accordingly, the battery pack canprevent the occurrence of gas generation due to breakage of the flexiblecasing or battery expansion which possibly damages an electronic device.

Next, the relationship between the flexible covering member and therigid covering member for achieving the above-mentioned state of bondingand others are described.

To bond the same type of materials, the strength can generally beincreased. To bond different type of materials, the strength level canbe achieved at a predetermined level or lower.

Further, by selecting a material which is melted at a temperature lowerthan the melting temperature of a bonding subject as the heat-bondinglayer and heating is conducted at a temperature at which the bondingsubject is not melted, the bonding strength can be controlled to be at apredetermined level or lower.

In an embodiment, by using these techniques in combination, basically, amaterial having a heat resistance, e.g., nylon is used in the outercovering layer of the flexible covering member, and a material which isdifferent from nylon and which is melted at a temperature at which nylonis not melted to exhibit bonding properties, e.g., cast polypropylene orEVA is used in the heat-bonding layer of the rigid covering member, thusachieving strength of the battery pack such that, as described above, ifexcess peel stresses are exerted on the laminated films upon drop of thebattery pack or the like, the laminated film of the flexible coveringmember is stretched and the rigid covering member is removed before apinhole or breakage is caused.

Thus, in an embodiment, it is preferred that the outer covering layer ofthe flexible covering member is composed of a material which isdifferent from the material for the heat-bonding layer of the rigidcovering member, and which includes solely or a combination of at leastone oriented resin material selected from the group consisting ofpolyolefin, polyamide, polyimide, and polyester.

When different materials are melted or only one material is melted,there is a tendency that a difference between the temperature at whichbonding starts and the temperature at which the both materials aremelted becomes smaller. The reason for this is that the battery itselfis a heat sink and continues taking heat and hence it is difficult tokeep the temperature of the melted heat-bonding layer constant.

This similarly occurs when the temperature of a heater is controlled inthe production of the battery pack.

For keeping the temperature of the sealing interface ideal during thebonding, heat transfer between the heating portion and the sealinginterface is required to be satisfactorily fast, and heat transfer ofthe inside of the interface is preferably slow to some extent tofacilitate heat storage.

In an embodiment, it is preferred that the outer covering layer andmetal layer stacked together in the rigid covering member have a thermalconductivity of 1,000 Wm⁻²K⁻¹ or more per area. In this case,satisfactory heat can be supplied to the heat-bonding layer.

With respect to the heat source used in bonding, specifically, heatsealing, by disposing a material having a thermal conductivity of 1 orless on the battery element side of the sealing interface, i.e., theinterface between the heat-bonding layer of the rigid covering memberand the outer covering layer of the flexible covering member, thetemperature of the sealing interface can be kept constant.

Particularly, the outer covering layer of the rigid covering member haspoor thermal conduction, and therefore, it is desired to select acombination of the outer covering layer having a thermal conductivity of1,050 Wm⁻²K⁻¹ or more per area and having a thickness of 100 μm or lessand the hard metal layer having a thermal conductivity of 50,000 Wm⁻²K⁻¹or more per area and having a thickness of 330 μm or less.

Thus, in an embodiment, as a material constituting the outer coveringlayer of the rigid covering member, polyamide (e.g., oriented nylon 6),polyester (e.g., polybutylene terephthalate, polyethylene terephthalate,or polyethylene naphthalate), polyolefin (e.g., oriented polypropyleneor oriented polyethylene), or the like is preferably used.

When the outer covering layer of the flexible covering member has athermal conductivity of 1 or less on the battery element side of thesealing interface, heat amount of the sealing interface is easier tocontrol. Further, it is preferred that a material having a meltingtemperature higher than the heat-bonding temperature of the rigidcovering member is selected for the outer covering layer of the flexiblecovering member.

As a material constituting the outer covering layer of the flexiblecovering member, polyamide (e.g., oriented nylon 6), polyester (e.g.,polybutylene terephthalate, polyethylene terephthalate, or polyethylenenaphthalate), or polyolefin (e.g., oriented polypropylene or orientedpolyethylene) is preferred.

By selecting the materials as described above, in embodiments, thecontact or integration of the flexible covering member and the rigidcovering member or a composite layer thereof can be achieved.

The production of a battery assembly is described again with referenceto the drawings. The casing member composed of the rigid laminated film41 described above is bonded with the battery 50.

First, as shown in FIG. 10A, the rigid laminated film 41 is folded sothat the battery 50 is wrapped in the rigid laminated film and the endsof the rigid laminated film 41 are touching on the top surface of thebattery 50.

Then, heater blocks are put on the top surface and bottom surface of thebattery 50 to heat the surfaces at such a temperature that the resinmaterial for the heat-bonding layer 74 is melted while applying apressure. The resin material is melted and serves as a bonding agent tobond the rigid laminated film 41 with the battery 50. In this instance,the heating is controlled so that the outer covering layer 62 of theflexible laminated film 57 is not melted, thus forming a batteryassembly 45 having a cross-section shown in FIG. 10B.

The temperature of the heater block varies depending on the type ofresin material for the heat-bonding layer 74, but it is a temperaturewhich is equal to or higher than the melting temperature of the resinmaterial for the heat-bonding layer and which is lower than the meltingtemperature of the material constituting the outer covering layer 62 ofthe flexible laminated film 57. By selecting a temperature in thisrange, the rigid laminated film can be bonded with the battery withoutmelting the resin material constituting the outer covering layer 62 ofthe flexible laminated film 57.

The rigid laminated film can be joined to or bonded with the batteryusing an adhesive or the like, but the joint using heat achieves higherresistance to peel stress continuously applied.

The heating temperature of higher than 120° C. seems to adversely affectthe battery element.

For example, polyethylene (PE) is frequently used in the separator forbattery element. The heating temperature of higher than 120° C. possiblylowers the safety or battery functions since PE has a meltingtemperature of about 120° C. Thus, it is desired that the upper limit ofthe temperature of the heater block used for heating is about 110° C.

As described above, in embodiments, the battery element 59 is sealed inthe flexible laminated film 57 during deaeration, so that the electrodesand the separator are fixed to one another due to atmospheric pressure,causing the whole of the battery element 59 to be a unified structure.

Further, the electrodes and separator are joined through a solidnon-aqueous electrolyte, and hence the structure has a resistance todrop impact/shock, for example, a phenomenon in which the wound layersor stacked layers in the battery element separate is unlikely to occur.

The device components are sealed while conducting deaeration and hencethe flexible laminated film 57 is closely fixed to the battery element59 due to atmospheric pressure, so that the resultant structure has ahigher resistance to external stresses than that of the individualunfixed components.

Further, in embodiments, the flexible laminated film and the rigidlaminated film can be joined together with bonding strength larger thanatmospheric pressure, and the joint of them is stronger than atmosphericpressure. Accordingly, under conditions such that a peel load forpeeling the flexible laminated film off the battery element is notexerted on the rigid laminated film, the rigid laminated film is unifiedwith the flexible laminated film and battery element by atmosphericpressure and functions as a battery pack housing having a resistance tobuckling caused in short drop or the like.

Instead of the structure shown in FIG. 10, the rigid laminated film mayhave any one of the structures shown in FIGS. 11 to 15.

In these structures, similarly, the heat-bonding layer 74 of the rigidlaminated film is melted and the outer covering layer 62 of the flexiblelaminated film is not melted.

FIGS. 11A and 11B show a structure of the battery assembly 45 in whichthe rigid laminated film 41 covers the bottom surface portion of thebattery 50 and the joint line of the ends of the rigid laminated film 41is positioned on the top surface portion of the battery assembly 45. Thebattery assembly shown in FIG. 10 is shaped so that the cross-sectionhas a rounded side portion, whereas the battery assembly shown in FIG.11 has a cross-section of a substantially rectangular form.

FIGS. 12A and 12B show a structure of the battery assembly 45 in whichthe rigid laminated film 41 covers one side portion of the battery 50and the joint line of the ends of the rigid laminated film 41 ispositioned on another side portion of the battery assembly 45.

FIGS. 13A and 13B show a structure of the battery assembly 45 in whichtwo rigid laminated films 41 respectively cover both side portions ofthe battery 50 and the joint lines of the ends of the rigid laminatedfilms 41 are respectively positioned on the top surface portion andbottom surface portion of the battery assembly 45.

FIG. 14A and FIG. 14B show a structure of the battery assembly 45 inwhich two rigid laminated films 41 respectively cover the top surfaceportion and bottom surface portion of the battery 50 and the joint linesof the ends of the rigid laminated films 41 are respectively positionedon both side portions of the battery assembly 45.

FIGS. 15A and 15B show a structure of the battery assembly 45 in whichthe rigid laminated film 41 is folded to cover the bottom portion of thebattery 50. FIG. 15B is a cross-sectional view as viewed from the sideof the battery assembly 45.

Fabrication of Battery Pack

Subsequently, the circuit board 44 is connected to the positiveelectrode terminal 55 a and negative electrode terminal 55 b (see FIG.3).

The positive electrode terminal 55 a and negative electrode terminal 55b extended from the top portion of the battery assembly 45 molded into apredetermined shape are welded to a protection circuit previouslymounted on the circuit board 44 by resistance welding, ultrasonicwelding, or the like.

The circuit board 44 connected to the battery element 59 is insertedinto a top cover 42 including an upper holder 42 a and a lower holder 42b which are molded in advance and fitted to each other.

The circuit board 44 is mounted thereon a protection circuit including atemperature protection element such as a fuse, a PTC, or a thermistor,an ID for identifying the battery pack, and a resistor, and is furtherformed a plurality of contact portions, to form the circuit board. Theprotection circuit is also used to a protection circuit including an ICfor monitoring the secondary battery and controlling a field effecttransistor (FET), and a protection circuit including a charge-dischargecontrol FET are used.

The PTC element is connected to the battery element in series. If thetemperature of the battery is higher than the preset temperature, thePTC element rapidly increases in electrical resistance to substantiallycut off the electric current flowing the battery. The fuse or thermistoris also connected to the battery element in series. If the temperatureof the battery is higher than the preset temperature, it cuts off theelectric current flowing the battery.

Overcharging, for example, exceeding 4.3 to 4.4 V of the secondarybattery terminal voltage, may result in heating or ignition of thebattery. Thus, the protection circuit including an IC for monitoring thesecondary battery and controlling the FET and a charge-discharge controlFET monitors the voltage of the secondary battery and switches off thecharge control FET to cut-off charging when exceeding 4.3 to 4.4 V.

Further, if the secondary battery is over-discharged until the terminalvoltage of the secondary battery becomes the discharge cut-off voltageor lower and the secondary battery voltage is 0 V, there is apossibility that the secondary battery suffers internalshort-circuiting, making it unable to recharge the battery. Thus, theprotection circuit monitors the secondary battery voltage and switchesoff the discharge control FET to cut-off discharging when the voltage islower than the discharge cut-off voltage.

The top and bottom of the circuit board 44 joined to the batteryassembly 45 are covered with the upper holder 42 a and lower holder 42 bpreviously molded by injection molding, and the lower holder 42 b isfitted to the upper holder 42 a, so that the circuit board is housed inthe top cover 42.

Then, the direction of the top cover 42 is changed so that the lowerholder 42 b is near the battery assembly 45, and the top cover 42 isfitted to the opening in the top portion of the battery assembly 45 sothat the positive electrode terminal 55 a and negative electrodeterminal 55 b are bent in the battery assembly 45.

Subsequently, the fitting portion of the top cover 42 and batteryassembly 45 is heated by a heater head to heat-seal the top cover 42 andbattery assembly 45. When the top cover 42 and the battery assembly 45is heat-sealed, the temperature of the heater head is higher than thetemperature in forming the battery assembly and equal to or higher thanthe melting temperature of the resin material for the sealant layer 73,and the top cover 42 is not bonded with the heat-bonding layer 74 butwith the sealant layer 73.

The heat-bonding layer 74 heated at the time of bonding the rigidlaminated film 41 and battery 50 is pushed by the top cover 42 uponfitting the top cover 42 and moved to the inside of the battery assembly45.

As described above, since a resin material having a melting temperaturelower than that of the sealant layer 73 is used as the heat-bondinglayer 74, only the heat-bonding layer 74 is melted at the time ofbonding the rigid laminated film 41 and battery 50. Thus, theheat-bonding layer 74 is moved without moving the sealant layer 73 usedfor bonding the top cover 42, making it possible to expose the sealantlayer 73.

When the top cover 42 and the battery assembly 45 are heat-sealed, abonding agent or a warmed resin material (hot-melt resin) may be putinto a space between the battery 50 and the top cover 42 as required. Inthis case, an inlet for bonding agent or hot-melt resin is previouslyformed in the top cover 42.

The use of a bonding agent or hot-melt resin further improves thebonding properties of the battery assembly 45 with the top cover 42. Inthe case of injecting a hot-melt resin, it is required that the circuitboard 44 does not suffer deformation or damage due to heat.

Subsequently, the rear cover 43 is fitted to the bottom portion of thebattery assembly 45, and the fitting portion of the rear cover 43 andbattery assembly 45 is heated by a heater head to heat-seal the rearcover 43 and battery assembly 45. In this case, like the top cover 42,the heat-bonding layer 74 is pushed by the rear cover 43 upon fittingthe rear cover 43 and moved to the inside of the battery assembly 45, sothat the exposed sealant layer 73 and the rear cover 43 are bonded witheach other.

When the rear cover 43 and the battery assembly 45 is head-sealed, as inthe case of the top cover 42, a bonding agent or a hot-melt resin may beput into a space between the battery 50 and the rear cover 43 asrequired. Also in this case, an inlet for bonding agent or hot-meltresin is previously formed in the rear cover 43. The steps for fittingand heat sealing the top cover 42 and rear cover 43 may be conductedsimultaneously.

With respect to the rear cover 43, a previously molded member can beused as described above. The rear cover also can be formed of a methodin which the battery assembly 45 is placed in a mold and a hot-meltresin is put into the bottom portion of the mold and molded togetherwith the battery assembly 45 into a unified shape.

When a resin material having good bonding properties with the top cover42 and rear cover 43 is formed as the sealant layer 73 on the inner sideof the metallic foil 71 and further the heat-bonding layer 74 using aresin material having good bonding properties with the outer coveringlayer 62 of the flexible laminated film 57 and having a meltingtemperature lower than that of the sealant layer 73 is formed on theinner side of the sealant layer 73 as described above, the battery 50can be firmly bonded with the rigid laminated film 41 and the batteryassembly 45 can be firmly bonded with the top cover 42 and rear cover43. Thus, the resultant battery pack 40 has a structure unlikely tosuffer damage.

Finally, a product label is attached to cover the joint line of the endsof the rigid laminated film 41 caused on part of the battery pack 40,thus obtaining a battery pack 40 shown in FIG. 2. The product label 46is optionally attached to the battery pack.

Instead of the product label 46, the rigid laminated film 41 can besubjected to printing, baking coating, or the like. For example, asshown in FIG. 16, a printing layer 77 on which desired patterns,characters, or the like are printed may be formed on the inner side (onthe metallic foil side) of the outer covering layer 72 of the rigidlaminated film 41 so that the printed patterns or characters may be seenthrough the outer covering layer 72.

In this case, the inversed patterns or characters are printed.Alternatively, as shown in FIG. 17, a baking coat 78 may be formed usinga laser or the like on the outer side of the metallic foil 71. In thiscase, the rigid laminated film has a structure such that the outercovering layer 72 and the bonding layer for bonding the outer coveringlayer 72 with the metallic foil 71 are not formed and the metallic foil71 having formed the baking coat 78 is exposed.

The battery pack 40 produced as described above can secure resistanceagainst external shock.

By using a metal material such as a rigid laminated film as a casing,even when the battery having a laminated casing is penetrated with anail, heat generation occurs only at the battery surface, and heatradiation is promoted. Accordingly heat generation in the battery can beprevented, thereby providing a safer battery pack.

Second Embodiment

In the second embodiment, a battery pack using a rigid laminated filmhaving a three-layer structure as a casing member is described.

The pack structure of the battery pack according to an embodiment ofpresent application is similar to that in the first embodiment shown inFIGS. 2 and 3. Further, the battery element and battery are similar tothose in the first embodiment, and thus the descriptions of them areomitted.

Fabrication of Battery Assembly

A battery 50 is covered with a rigid laminated film 80 having athree-layer structure shown in FIG. 18 to fabricate a battery assembly.First, the structure of the rigid laminated film 80 is described.

As shown in FIG. 18, the rigid laminated film 80 in the secondembodiment is composed of a multilayer film having a moisture resistanceand insulation properties, and including a metallic foil designated byreference numeral 81 sandwiched between an outer covering layer 82composed of a resin film and a heat-bonding layer 83.

As materials for the metallic foil 81 and outer covering layer 82,materials similar to those in the first embodiment can be used.

The metallic foil 81 and the outer covering layer 82, and the metallicfoil 81 and the heat-bonding layer 83 are individually bonded throughbonding agent layers 84 and 85, respectively.

The heat-bonding layer 83 is used for bonding the battery 50 coveredwith the flexible laminated film 57 and the rigid laminated film 80without using a separate member for bonding.

In the second embodiment, a material having good bonding properties witha resin used in the outer covering layer 62 of the battery 50 such asNy, PET, or PEN, and with a resin used as a material for the top cover42 and rear cover 43 such as PP, and having high reactivity is used inthe heat-bonding layer 83, and therefore a battery pack can be producedwithout the sealant layer 73 formed in the first embodiment.

With respect to the above material, specifically, acid-modifiedpolypropylene, an ionomer resin, an ethylene-vinyl acetate copolymer, anethylene-acrylic acid copolymer, an ethyl acrylate copolymer, a methylacrylate copolymer, a methacrylic acid copolymer, a methyl methacrylatecopolymer, polyacrylonitrile, an ethylene-vinyl alcohol resin,polyamide, polyester, or the like can be used. Of these, especiallypreferred is acid-modified polypropylene, an ionomer resin, or anethylene-vinyl alcohol resin. These materials may be used as a hot-meltadhesive or film or a weathering-resistant adhesive.

In the rigid laminated film 80 in the second embodiment, theheat-bonding layer 83 has a thickness of about 25 to 50 μm. The metallicfoil 81 and outer covering layer 82 may individually have thicknessesequivalent to those in the first embodiment. In the rigid laminated film41 in the first embodiment, the heat-bonding layer 74 has a thickness of1 to 5 μm, but, in the second embodiment, the heat-bonding layer 83 hasa larger thickness and hence, the heat-bonding layer 83 itself exhibitsa cushioning effect to improve the bonding properties.

The casing member formed of the rigid laminated film 80 is bonded withthe battery 50. As in the case of the first embodiment, the rigidlaminated film 80 is folded so that the battery 50 is wrapped in therigid laminated film to touch the end of the rigid laminated film 80 atthe top surface of the battery 50.

Then, heater blocks are put on the top surface and bottom surface of thebattery 50 to heat the surfaces at such a temperature that the resinmaterial for the heat-bonding layer 83 is melted while applying apressure. The resin material is melted and serves as a bonding agent tobond the rigid laminated film 80 with the battery 50. When bonding therigid laminated film 80 with the battery 50, as in the case of the firstembodiment, the outer covering layer 62 of the flexible laminated filmis subjected to a process so as not to melt, thus forming a batteryassembly 45.

The temperature of the heater block varies depending on the type ofresin material for the heat-bonding layer, but it may be equal to orhigher than the melting temperature of the resin material for theheat-bonding layer 83. The heating temperature of higher than 120° C. isconsidered to adversely affect the battery element 59. From this pointof view, it is desired that the upper limit of the temperature of theheater block used for heating is about 110° C.

Fabrication of Battery Pack

Next, the circuit board 44 is connected to the positive electrodeterminal 55 a and negative electrode terminal 55 b. A method forconnecting the positive electrode terminal 55 a and negative electrodeterminal 55 b to the circuit board 44 is the same as that in the firstembodiment, and therefore the descriptions are omitted.

The top cover 42 containing therein the circuit board 44 is fitted tothe opening of the battery assembly 45 on the top side. Then, thefitting portion of the top cover 42 is heated by a beater head toheat-seal the top cover 42 and battery assembly 45.

In the present embodiment, as the resin material for the heat-bondinglayer 83, a resin material having good bonding properties with the topcover 42 and rear cover 43 is used, and therefore the top cover 42 isbonded with the heat-bonding layer 83. In addition, like the top cover42, the rear cover 43 can be similarly bonded with the battery assembly45.

In this instance, a bonding agent or a warmed resin material (hot-meltresin) may be put into a space between the battery 50 and the top cover42 as required. In this case, inlets for bonding agent or hot-melt resinare previously formed in the top cover and rear cover. The injection ofa bonding agent or hot-melt resin further improves the bondingproperties of the battery assembly 45 with the top cover 42 and rearcover 43. In the case of injecting a hot-melt resin from the top cover42, it is required that the circuit board does not suffer deformation ordamage due to heat.

With respect to the rear cover 43, a previously molded member can beused as described above. Alternatively, the rear cover can be formed ofa method in which the battery assembly 45 is placed in a mold and ahot-melt resin is put into the bottom portion of the mold and moldedtogether with the battery assembly 45 into a unified shape.

Hereinabove, the battery pack 40 according to the second embodimentusing the rigid laminated film 80 having a three-layer structure as acasing member is described.

There can be provided a battery pack having excellent effect of thebattery pack according to the first embodiment exhibited upon the dropand the like. A safer battery pack having a secure resistance againstexternal shock is provided by appropriately selecting a resin materialused in the heat-bonding layer 83 and it has satisfactory moisturepenetration resistance and heat release property even if a sealant layeris provided.

Third Embodiment

FIGS. 19A to 19C show a battery pack according to another embodiment.

FIGS. 19A to 19C and FIGS. 20A and 20B are diagrammatic views showing abattery in the battery pack according to another embodiment, which is inthe process of fabrication.

In another embodiment, using a flexible laminated film 31 having arecessed portion 31 a and a rigid laminated film 32, a principal portionof a battery element, i.e., a portion of a battery element 35constituting a hexahedron, excluding one principal surface, is coveredwith the flexible laminated film 31 so that the battery element 35 ishoused in the recessed portion 31 a (see FIG. 20).

Then, the rigid laminated film 32 is positioned so that it covers theremaining portion of the battery element 35, i.e., one principal surfaceof the battery element 35, typically, the opening of the recessedportion 31 a, and the stacked flexible laminated film 31 and rigidlaminated film 32 around the battery element 35 are sealed. In thisinstance, heat sealing wider a reduced pressure is similar to that inthe first embodiment, and the battery element 35 adheres to the flexiblelaminated film 31 and rigid laminated film 32 by the heat sealing undera reduced pressure.

As shown in FIG. 20B, the rigid laminated film 32 and flexible laminatedfilm 31 are shaped so that they cover the battery element 35, but, inthis embodiment, a heat-bonding resin tape 90 is prepared, and the tape90 is disposed between the outer covering layer of the folded flexiblelaminated film 31 and the outer covering layer of the flexible laminatedfilm 31 covering the battery element 35 and melted to bond togetherthese flexible laminated films.

Simultaneously, the heat-bonding layer of the rigid laminated film 32 ismelted and bonded with the heat-bonding layer of the folded flexiblelaminated film 31. In this instance, the outer covering layer of theflexible laminated film 31 is subjected to a process so as not to melt.The heat-bonding resin tape 90 may have a substrate, as in the case ofthe first embodiment.

Then, a circuit board (not shown) and resin molded covers are providedto produce a battery pack having the rigid laminated film 32 as theoutermost layer. The battery pack produced has not only good volumeefficiency and high battery strength but also excellent effect of thebattery pack according to the first embodiment exhibited upon the dropand the like.

Fourth Embodiment

FIGS. 21A and 21B are cross-sectional views showing a battery packaccording to still another embodiment, which is in the process offabrication.

The battery pack according to the present embodiment has a structuresimilar to that of the battery pack according to the third embodiment,but the flexible laminated film 31 has both sides shorter than those inthe third embodiment (FIG. 21A).

As in the case of the third embodiment, the laminated films around thebattery element 35 are sealed, and then, as shown in FIG. 21B, the rigidlaminated film 32 and flexible laminated film 31 are shaped so that theycover the battery element 35. In the present embodiment, a heat-bondingresin tape 90 is prepared, and the tape 90 is disposed between theheat-bonding layer of the folded rigid laminated film 32 and the outercovering layer of the flexible laminated film 31 covering the batteryelement 35 and melted to bond together these films. In this instance, asin the case of the first embodiment, the rigid laminated film and theflexible laminated film are bonded with an adhesive strength equal to orhigher than atmospheric pressure and with a peel strength equal to orlower than a breaking strength of the flexible laminated film. Forexample, the heat-bonding resin tape 90 is melted while the outercovering layer of the flexible laminated film 31 is not melted. Theheat-bonding resin tape 90 may have a substrate.

The battery pack according to the present embodiment has excellenteffect of the battery pack according to the first embodiment exhibitedupon the drop and the like.

In the present embodiment, instead of the heat-bonding resin tape 90, aso-called adhesive double-faced tape can be used, and, in this case,bonding at low temperatures is possible.

Fifth Embodiment

FIGS. 22A and 22B are cross-sectional views showing a battery packaccording to still further another embodiment, which is being produced.

The battery pack according to the present embodiment has a structuresimilar to that of the battery pack according to the third embodiment,but the flexible laminated film 31 has both sides shorter than those inthe third embodiment (FIG. 22A).

As in the case of the third embodiment, the laminated films around thebattery element 35 are sealed, and then, as shown in FIG. 22B, the rigidlaminated film 32 and flexible laminated film 31 are shaped so that theycover the battery element 35, but, in the present embodiment, theheat-bonding layer of the folded rigid laminated film 32 is melted andbonded with the outer covering layer of the flexible laminated film 31covering the battery element 35. In this instance, as in the case of thefirst embodiment, the rigid laminated film and the flexible laminatedfilm are bonded with an adhesive strength equal to or higher thanatmospheric pressure and with a peel strength equal to or lower than abreaking strength of the flexible laminated film. For example, theheat-bonding layer of the rigid laminated film 32 is melted while theouter covering layer of the flexible laminated film 31 is not melted.

The battery pack according to the present embodiment has excellenteffect of the battery pack according to the first embodiment exhibitedupon the drop and the like.

In the present embodiment, an acryl ester, silicone, or latex adhesivecan be used for bonding the outer covering layer of the folded rigidlaminated film 32 and the outer covering layer of the flexible laminatedfilm 31 covering the battery element 35, and, in this case, bonding atlow temperatures is possible.

EXAMPLES

Hereinbelow, the present application will be described in more detailwith reference to the following Examples and Comparative Examples, whichshould not be construed as limiting the scope.

Examples 1-1 to 23-5 and Comparative Examples 1 to 4

Battery packs having structures and properties shown in Tables 1 to 4below were individually prepared by the above-described procedure. Withrespect to each of the battery packs obtained, evaluations ofperformance shown below were conducted, and the results are shown inTables 5 to 8.

(a) Adhesive Strength Test

With respect to each of the Examples and Comparative Examples, anadhesive strength between the flexible covering member and the bondinglayer was measured. The measurement was conducted by folding both endsof the pack casing including the bonding layer and stacking them andperforming a tensile test in the direction perpendicular to the surfaceof the battery.

(b) Peel Strength Test

With respect to each of the Examples and Comparative Examples, a peelstrength between the flexible covering member and the bonding layer wasmeasured. The measurement was conducted by peeling one end of the packcasing including the bonding layer.

A peel strength was measured in accordance with the method described inJIS K6854-2 (Determination of peel strength of bonded assemblies—Part 2:180° peel).

(c) Drop Test 1

The battery packs in the Examples and Comparative Examples wereindividually dropped in an arbitrary position from a height of 1.5meters ten times, and then checked whether the battery pack was able tobe fitted into a portable electric device without any problems and wasable to be charged and used without lowering of the functions. It isrequired that the battery pack have a design such that both theelectricity generating elements and the casing are basically not damagedin the drop from that height and the resultant battery pack besubsequently usable as a battery pack.

(d) Drop Test 2

The battery packs in the Examples and Comparative Examples wereindividually dropped in an arbitrary position from a height of 10meters, and then checked that the battery pack was unable to be fittedinto a portable electric device, the battery element was not damaged,and the battery casing was not damaged.

It is required that the battery have a design such that the battery isnot damaged unless air goes into the battery from the outside, thecasing is possibly damaged, and the pack housing absorbs theimpact/shock to protect the device from the impact/shock.

In this test, a battery pack such that the battery pack was unable to beused and the battery body or battery casing was not damaged passed thetest, and a battery pack such that the battery pack had no malfunctionsand the battery body or battery casing was damaged did not pass thetest.

TABLE 1 Outer covering Metal layer layer of rigid of rigid Adhesive Peelcovering Thermal covering strength strength member Thicknessconductivity member Thickness MPa N/mm Material μm Wm⁻²K⁻¹ Material μmEx. 0.20 2.22 Polyethylene 12 50,000 Aluminum 100 1-1 terephthalate Ex.0.18 2.00 Polybutylene 12 50,000 Aluminum 100 1-2 terephthalate Ex. 0.161.8 Polyethylene 12 50,000 Aluminum 100 1-3 naphthalate Ex. 0.14 1.6Oriented nylon 6 25 8,400 Aluminum 100 1-4 Ex. 0.15 1.7 Oriented 2513,200 Aluminum 100 1-5 polyethylene Ex. 0.12 1.3 Oriented 25 4,800Aluminum 100 1-6 polypropylene Ex. 0.39 4.3 None (Only 2 500,000Aluminum 100 1-7 protective layer) Ex. 0.20 2.2 Polyethylene 12 50,000Copper 100 2-1 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Iron100 2-2 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Nickel- 1002-3 terephthalate plated iron Ex. 0.20 2.2 Polyethylene 12 50,000 Nickel100 2-4 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Tin-plated 1002-5 terephthalate iron Ex. 0.20 2.2 Polyethylene 12 50,000 Zinc-plated100 2-6 terephthalate iron Ex. 0.20 2.2 Polyethylene 12 50,000 Stainless100 2-7 terephthalate steel Ex. 3 0.11 1.2 Oriented 115 1,043 Aluminum100 polypropylene Ex. 4 0.10 1.1 Oriented 115 1,043 Stainless 330polypropylene steel Ex. 0.18 2.0 Polyethylene 12 50,000 Aluminum 100 5-1terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-2terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 5-3terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-4terephthalate Ex. 0.19 2.1 Polyethylene 12 50,000 Aluminum 100 5-5terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 5-6terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-7terephthalate Ex. 0.40 4.4 Polyethylene 12 50,000 Aluminum 100 5-8terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-9terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-10terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 5-11terephthalate Ex. 0.45 5.4 Polyethylene 12 50,000 Aluminum 100 5-12terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 6-1terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 6-2terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 6-3terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 6-4terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 6-5terephthalate Com. 0.05 0.6 Oriented 150 800 Stainless 400 Ex. 1polypropylene steel Com. 0.53 5.7 Polyethylene 12 50,000 Aluminum 100Ex. 2 terephthalate Com. 0.52 5.7 Battery sealed Ex. 3 in soft casing isfixed to molded case with adhesive double-faced tape Com. 0.17 2.1Polyethylene 12 50,000 Aluminum 100 Ex. 4 terephthalate Rigid coveringmember Outer covering layer + Outer Vacuum metal covering (Adhesionlayer layer of of Thermal Thermal flexible casing conductivityconductivity covering and Wm⁻²K⁻¹ Wm⁻²K⁻¹ Bonding layer member device)Ex. 2,300,000 48,940 EVA on Nylon Vacuum 1-1 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 1-2 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 1-3 polypropylene surface Ex.2,300,000 8,369 EVA on Nylon Vacuum 1-4 polypropylene surface Ex.2,300,000 13,125 EVA on Nylon Vacuum 1-5 polypropylene surface Ex.2,300,000 4,790 EVA on Nylon Vacuum 1-6 polypropylene surface Ex.2,300,000 410,714 EVA on Nylon Vacuum 1-7 polypropylene surface Ex.3,900,000 49,367 EVA on Nylon Vacuum 2-1 polypropylene surface Ex.900,000 47,368 EVA on Nylon Vacuum 2-2 polypropylene surface Ex. 950,00047,500 EVA on Nylon Vacuum 2-3 polypropylene surface Ex. 1,000,00047,619 EVA on Nylon Vacuum 2-4 polypropylene surface Ex. 850,000 47,222EVA on Nylon Vacuum 2-5 polypropylene surface Ex. 1,000,000 47,619 EVAon Nylon Vacuum 2-6 polypropylene surface Ex. 150,000 37,500 EVA onNylon Vacuum 2-7 polypropylene surface Ex. 3 2,300,000 1,043 EVA onNylon Vacuum polypropylene surface Ex. 4 45,455 1,020 EVA on NylonVacuum polypropylene surface Ex. 2,300,000 48,936 Ethylene- Nylon Vacuum5-1 acrylic acid copolymer Ex. 2,300,000 48,936 Ethyl acrylate NylonVacuum 5-2 copolymer Ex. 2,300,000 48,936 Methyl Nylon Vacuum 5-3acrylate copolymer Ex. 2,300,000 48,936 Methacrylic Nylon Vacuum 5-4acid copolymer Ex. 2,300,000 48,936 Methyl Nylon Vacuum 5-5 methacrylatecopolymer Ex. 2,300,000 48,936 Polyacrylonitrile Nylon Vacuum 5-6 Ex.2,300,000 48,936 Ethylene-vinyl Nylon Vacuum 5-7 alcohol resin Ex.2,300,000 48,936 Polyamide hot- Nylon Vacuum 5-8 melt Ex. 2,300,00048,936 Polyester hot- Nylon Vacuum 5-9 melt Ex. 2,300,000 48,936Acid-modified Nylon Vacuum 5-10 polypropylene Ex. 2,300,000 48,936Ionomer Nylon Vacuum 5-11 Ex. 2,300,001 48,936 Adhesive Nylon Vacuum5-12 double-faced tape Ex. 2,300,000 48,936 EVA on Polyethylene Vacuum6-1 polypropylene terephthalate surface Ex. 2,300,000 48,936 EVA onPolybutylene Vacuum 6-2 polypropylene terephthalate surface Ex.2,300,000 48,936 EVA on Polyethylene Vacuum 6-3 polypropylenenaphthalate surface Ex. 2,300,000 48,936 EVA on Oriented Vacuum 6-4polypropylene polypropylene surface Ex. 2,300,000 48,936 EVA on OrientedVacuum 6-5 polypropylene polyethylene surface Com. 37,500 783 EVA onNylon Vacuum Ex. 1 polypropylene surface Com. 2,300,000 48,940 Polyamidehot- Heated Vacuum Ex. 2 melt until nylon is melted Com. — High-strengthNylon Vacuum Ex. 3 adhesive double-faced tape Com. 2,300,000 48,940 EVAon Nylon No Ex. 4 polypropylene vacuum surface (EVA: ethylene-vinylacetate copolymer)

TABLE 2 Resins in composite layer Outer covering layer (hard)/Bondinglayer/ Outer covering layer Metal in Adhesive Peel (soft) Total Thermalcomposite strength strength Material and thickness conductivity layerThickness MPa N/mm thickness/μm μm Wm⁻²K⁻¹ Material μm Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 7-1 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polybutylene 87 1,690 Aluminum135 7-2 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 7-3 naphthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Nylon 15/Cast 90 1,556 Aluminum135 7-4 polypropylene 60/Nylon 15 Ex. 0.12 1.3 Oriented polyethylene 1001,545 Aluminum 135 7-5 25/ Cast polypropylene 60/Nylon 15 Ex. 0.11 1.2Oriented polypropylene 100 1,282 Aluminum 135 7-6 25/ Cast polypropylene60/Nylon 15 Ex. 0.11 1.6 Polyethylene 87 1,690 Copper 135 8-1terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.11 1.2Polyethylene 87 1,690 Iron 135 8-2 terephthalate 12/ Cast polypropylene60/Nylon 15 Ex. 0.11 1.2 Polyethylene 87 1,690 Nickel- 135 8-3terephthalate 12/ plated iron Cast polypropylene 60/Nylon 15 Ex. 0.111.2 Polyethylene 87 1,690 Nickel 135 8-4 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.11 1.2 Polyethylene 87 1,690 Tin-plated135 8-5 terephthalate 12/ iron Cast polypropylene 60/Nylon 15 Ex. 0.111.2 Polyethylene 87 1,690 Zinc-plated 135 8-6 terephthalate 12/ ironCast polypropylene 60/Nylon 15 Ex. 0.11 1.2 Polyethylene 87 1,690Stainless 135 8-7 terephthalate 12/ steel Cast polypropylene 60/Nylon 15Ex. 9 0.10 1.1 Polyethylene 87 1,690 Aluminum 335 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-1 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 10-2 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-3 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 10-4 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-5 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 10-6 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-7 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.40 4.4Polyethylene 87 1,690 Aluminum 135 10-8 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-9 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 10-10 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 10-11 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.45 5.0Polyethylene 87 1,690 Aluminum 135 10-12 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 11-1 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 11-2 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 11-3 terephthalate 12/ Cast polypropylene 60/Nylon 15 Ex. 0.12 1.3Polyethylene 87 1,690 Aluminum 135 11-4 terephthalate 12/ Castpolypropylene 60/Nylon 15 Ex. 0.12 1.3 Polyethylene 87 1,690 Aluminum135 11-5 terephthalate 12/ Cast polypropylene 60/Nylon 15 Whole Outercomposite covering layer layer of Thermal Thermal flexible conductivityconductivity covering Wm⁻²K⁻¹ Wm⁻²K⁻¹ Adhesive tape member Vacuum Ex.1,703,704 1,688 EVA on Nylon Vacuum 7-1 polyethylene surface Ex.1,703,704 1,688 EVA on Nylon Vacuum 7-2 polyethylene surface Ex.1,703,704 1,688 EVA on Nylon Vacuum 7-3 polyethylene surface Ex.1,703,704 1,555 EVA on Nylon Vacuum 7-4 polyethylene surface Ex.1,703,704 1,544 EVA on Nylon Vacuum 7-5 polyethylene surface Ex.1,703,704 1,281 EVA on Nylon Vacuum 7-6 polyethylene surface Ex.2,888,889 1,689 EVA on Nylon Vacuum 8-1 polyethylene surface Ex. 666,6671,686 EVA on Nylon Vacuum 8-2 polyethylene surface Ex. 666,667 1,686 EVAon Nylon Vacuum 8-3 polyethylene surface Ex. 740,741 1,686 EVA on NylonVacuum 8-4 polyethylene surface Ex. 629,630 1,685 EVA on Nylon Vacuum8-5 polyethylene surface Ex. 740,741 1,686 EVA on Nylon Vacuum 8-6polyethylene surface Ex. 111,111 1,665 EVA on Nylon Vacuum 8-7polyethylene surface Ex. 9 686,567 1,686 EVA on Nylon Vacuumpolyethylene surface Ex. 1,703,704 1,688 Ethylene- Nylon Vacuum 10-1acrylic acid copolymer Ex. 1,703,704 1,688 Ethyl acrylate Nylon Vacuum10-2 copolymer Ex. 1,703,704 1,688 Methyl Nylon Vacuum 10-3 acrylatecopolymer Ex. 1,703,704 1,688 Methacrylic Nylon Vacuum 10-4 acidcopolymer Ex. 1,703,704 1,688 Methyl Nylon Vacuum 10-5 methacrylatecopolymer Ex. 1,703,704 1,688 Polyacrylonitrile Nylon Vacuum 10-6 Ex.1,703,704 1,688 Ethylene-vinyl Nylon Vacuum 10-7 alcohol resin Ex.1,703,704 1,688 Polyamide hot- Nylon Vacuum 10-8 melt Ex. 1,703,7041,688 Polyester hot- Nylon Vacuum 10-9 melt Ex. 1,703,704 1,688Acid-modified Nylon Vacuum 10-10 polypropylene Ex. 1,703,704 1,688Ionomer Nylon Vacuum 10-11 Ex. 1,703,704 1,688 Adhesive Nylon Vacuum10-12 double-faced tape Ex. 1,703,704 1,688 EVA on Polyethylene Vacuum11-1 polyethylene terephthalate surface Ex. 1,703,704 1,688 EVA onPolybutylene Vacuum 11-2 polyethylene terephthalate surface Ex.1,703,704 1,688 EVA on Polyethylene Vacuum 11-3 polyethylene naphthalatesurface Ex. 1,703,704 1,688 EVA on Oriented Vacuum 11-4 polyethylenepolypropylene surface Ex. 1,703,704 1,688 EVA on Oriented Vacuum 11-5polyethylene polyethylene surface (EVA: ethylene-vinyl acetatecopolymer)

TABLE 3 Metal layer Outer covering of rigid Adhesive Peel layer of rigidThermal covering strength strength covering member Thicknessconductivity member Thickness MPa N/nm Material μm Wm⁻²K⁻¹ Material μmEx. 0.19 2.1 Polyethylene 12 50,000 Aluminum 100 12-1 terephthalate Ex.0.17 1.9 Polybutylene 12 50,000 Aluminum 100 12-2 terephthalate Ex. 0.151.7 Polyethylene 12 50,000 Aluminum 100 12-3 naphthalate Ex. 0.13 1.4Oriented nylon 6 25 8,400 Aluminum 100 12-4 Ex. 0.14 1.6 Oriented 2513,200 Aluminum 100 12-5 polyethylene Ex. 0.11 1.2 Oriented 25 4,800Aluminum 100 12-6 polypropylene Ex. 0.38 4.2 None (Only 2 500,000Aluminum 100 12-7 protective layer) Ex. 0.19 2.1 Polyethylene 12 50,000Copper 100 13-1 terephthalate Ex. 0.19 2.1 Polyethylene 12 50,000 Iron100 13-2 terephthalate Ex. 0.19 2.1 Polyethylene 12 50,000 Nickel-plated100 13-3 terephthalate iron Ex. 0.19 2.1 Polyethylene 12 50,000 Nickel100 13-4 terephthalate Ex. 0.19 2.1 Polyethylene 12 50,000 Tin-plated100 13-5 terephthalate iron Ex. 0.19 2.1 Polyethylene 12 50,000Zinc-plated 100 13-6 terephthalate iron Ex. 0.19 2.1 Polyethylene 1250,000 Stainless 100 13-7 terephthalate steel Ex. 14 0.10 1.1 Oriented115 1,043 Aluminum 100 polypropylene Ex. 15 0.09 1.0 Oriented 115 1,043Aluminum 330 polypropylene Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum100 16-1 terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 10016-2 terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 16-3terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 100 16-4terephthalate Ex. 0.18 2.0 Polyethylene 12 50,000 Aluminum 100 16-5terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 16-6terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 100 16-7terephthalate Ex. 0.39 4.3 Polyethylene 12 50,000 Aluminum 100 16-8terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 100 16-9terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 100 16-10terephthalate Ex. 0.15 1.7 Polyethylene 12 50,000 Aluminum 100 16-11terephthalate Ex. 0.44 4.9 Polyethylene 12 50,000 Aluminum 100 16-12terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 17-1terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 17-2terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 17-3terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 17-4terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 17-5terephthalate Rigid covering member Outer covering layer + Outer metalcovering layer layer of Thermal Thermal flexible conductivityconductivity covering Wm⁻²K⁻¹ Wm⁻²K⁻¹ Adhesive tape member Vacuum Ex.2,300,000 48,940 EVA on Nylon Vacuum 12-1 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 12-2 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 12-3 polypropylene surface Ex.2,300,000 8,369 EVA on Nylon Vacuum 12-4 polypropylene surface Ex.2,300,000 13,125 EVA on Nylon Vacuum 12-5 polypropylene surface Ex.2,300,000 4,790 EVA on Nylon Vacuum 12-6 polypropylene surface Ex.2,300,000 410,714 EVA on Nylon Vacuum 12-7 polypropylene surface Ex.3,900,000 49,367 EVA on Nylon Vacuum 13-1 polypropylene surface Ex.900,000 47,368 EVA on Nylon Vacuum 13-2 polypropylene surface Ex.950,000 47,500 EVA on Nylon Vacuum 13-3 polypropylene surface Ex.1,000,000 47,619 EVA on Nylon Vacuum 13-4 polypropylene surface Ex.850,000 47,222 EVA on Nylon Vacuum 13-5 polypropylene surface Ex.1,000,000 47,619 EVA on Nylon Vacuum 13-6 polypropylene surface Ex.150,000 37,500 EVA on Nylon Vacuum 13-7 polypropylene surface Ex. 142,300,000 1,043 EVA on Nylon Vacuum polypropylene surface Ex. 15 696,9701,042 EVA on Nylon Vacuum polypropylene surface Ex. 2,300,000 48,936Ethylene- Nylon Vacuum 16-1 acrylic acid copolymer Ex. 2,300,000 48,936Ethyl acrylate Nylon Vacuum 16-2 copolymer Ex. 2,300,000 48,936 Methylacrylate Nylon Vacuum 16-3 copolymer Ex. 2,300,000 48,936 MethacrylicNylon Vacuum 16-4 acid copolymer Ex. 2,300,000 48,936 Methyl NylonVacuum 16-5 methacrylate copolymer Ex. 2,300,000 48,936Polyacrylonitrile Nylon Vacuum 16-6 Ex. 2,300,000 48,936 Ethylene-vinylNylon Vacuum 16-7 alcohol resin Ex. 2,300,000 48,936 Polyamide hot-Nylon Vacuum 16-8 melt Ex. 2,300,000 48,936 Polyester hot- Nylon Vacuum16-9 melt Ex. 2,300,000 48,936 Acid-modified Nylon Vacuum 16-10polypropylene Ex. 2,300,000 48,936 Ionomer Nylon Vacuum 16-11 Ex.2,300,001 48,936 Adhesive Nylon Vacuum 16-12 double-faced tape Ex.2,300,000 48,936 EVA on Polyethylene Vacuum 17-1 polypropyleneterephthalate surface Ex. 2,300,000 48,936 EVA on Polybutylene Vacuum17-2 polypropylene terephthalate surface Ex. 2,300,000 48,936 EVA onPolyethylene Vacuum 17-3 polypropylene naphthalate surface Ex. 2,300,00048,936 EVA on Oriented Vacuum 17-4 polypropylene polypropylene surfaceEx. 2,300,000 48,936 EVA on Oriented Vacuum 17-5 polypropylenepolyethylene surface (EVA: ethylene-vinyl acetate copolymer) EVA oradhesive double-faced tape is disposed only at a portion opposite theflexible covering material surface.

TABLE 4 Metal layer Outer covering of rigid Adhesive Peel layer of rigidThermal covering strength strength covering member Thicknessconductivity member Thickness MPa N/nm Material μm Wm⁻²K⁻¹ Material μmEx. 0.20 2.2 Polyethylene 12 50,000 Aluminum 100 18-1 terephthalate Ex.0.18 2.0 Polybutylene 12 50,000 Aluminum 100 18-2 terephthalate Ex. 0.161.8 Polyethylene 12 50,000 Aluminum 100 18-3 naphthalate Ex. 0.14 1.6Oriented nylon 6 25 8,400 Aluminum 100 18-4 Ex. 0.15 1.7 Oriented 2513,200 Aluminum 100 18-5 polyethylene Ex. 0.12 1.3 Oriented 25 4,800Aluminum 100 18-6 polypropylene Ex. 0.39 4.3 None (Only 2 500,000Aluminum 100 18-7 protective layer) Ex. 0.20 2.2 Polyethylene 12 50,000Copper 100 19-1 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Iron100 19-2 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Nickel-plated100 19-3 terephthalate iron Ex. 0.20 2.2 Polyethylene 12 50,000 Nickel100 19-4 terephthalate Ex. 0.20 2.2 Polyethylene 12 50,000 Tin-plated100 19-5 terephthalate iron Ex. 0.20 2.2 Polyethylene 12 50,000Zinc-plated 100 19-6 terephthalate iron Ex. 0.20 2.2 Polyethylene 1250,000 Stainless 100 19-7 terephthalate steel Ex. 20 0.11 1.2 Oriented115 1,043 Aluminum 100 polypropylene Ex. 21 0.10 1.1 Oriented 115 1,043Aluminum 330 polypropylene Ex. 0.18 2.0 Polyethylene 12 50,000 Aluminum100 22-1 terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 10022-2 terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 22-3terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 22-4terephthalate Ex. 0.19 2.1 Polyethylene 12 50,000 Aluminum 100 22-5terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 22-6terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 22-7terephthalate Ex. 0.40 4.4 Polyethylene 12 50,000 Aluminum 100 22-8terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 22-9terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 22-10terephthalate Ex. 0.16 1.8 Polyethylene 12 50,000 Aluminum 100 22-11terephthalate Ex. 0.45 5.6 Polyethylene 12 50,000 Aluminum 100 22-12terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 23-1terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 23-2terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 23-3terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 23-4terephthalate Ex. 0.17 1.9 Polyethylene 12 50,000 Aluminum 100 23-5terephthalate Rigid covering member Outer covering Outer layer +covering metal layer layer of Thermal Thermal flexible conductivityconductivity covering Wm⁻²K⁻¹ Wm⁻²K⁻¹ Bonding layer member Vacuum Ex.2,300,000 48,940 EVA on Nylon Vacuum 18-1 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 18-2 polypropylene surface Ex.2,300,000 48,936 EVA on Nylon Vacuum 18-3 polypropylene surface Ex.2,300,000 8,369 EVA on Nylon Vacuum 18-4 polypropylene surface Ex.2,300,000 13,125 EVA on Nylon Vacuum 18-5 polypropylene surface Ex.2,300,000 4,790 EVA on Nylon Vacuum 18-6 polypropylene surface Ex.2,300,000 410,714 EVA on Nylon Vacuum 18-7 polypropylene surface Ex.3,900,000 49,367 EVA on Nylon Vacuum 19-1 polypropylene surface Ex.900,000 47,368 EVA on Nylon Vacuum 19-2 polypropylene surface Ex.950,000 47,500 EVA on Nylon Vacuum 19-3 polypropylene surface Ex.1,000,000 47,619 EVA on Nylon Vacuum 19-4 polypropylene surface Ex.850,000 47,222 EVA on Nylon Vacuum 19-5 polypropylene surface Ex.1,000,000 47,619 EVA on Nylon Vacuum 19-6 polypropylene surface Ex.150,000 37,500 EVA on Nylon Vacuum 19-7 polypropylene surface Ex. 202,300,000 1,043 EVA on Nylon Vacuum polypropylene surface Ex. 21 696,9701,042 EVA on Nylon Vacuum polypropylene surface Ex. 2,300,000 48,936Ethylene-acrylic Nylon Vacuum 22-1 acid copolymer Ex. 2,300,000 48,936Ethyl acrylate Nylon Vacuum 22-2 copolymer Ex. 2,300,000 48,936 Methylacrylate Nylon Vacuum 22-3 copolymer Ex. 2,300,000 48,936 Methacrylicacid Nylon Vacuum 22-4 copolymer Ex. 2,300,000 48,936 Methyl NylonVacuum 22-5 methacrylate copolymer Ex. 2,300,000 48,936Polyacrylonitrile Nylon Vacuum 22-6 Ex. 2,300,000 48,936 Ethylene-vinylNylon Vacuum 22-7 alcohol resin Ex. 2,300,000 48,936 Polyamide hot-Nylon Vacuum 22-8 melt Ex. 2,300,000 48,936 Polyester hot- Nylon Vacuum22-9 melt Ex. 2,300,000 48,936 Acid-modified Nylon Vacuum 22-10polypropylene Ex. 2,300,000 48,936 Ionomer Nylon Vacuum 22-11 Ex.2,300,001 48,936 Adhesive on Nylon Vacuum 22-12 polypropylene surfaceEx. 2,300,000 48,936 EVA on Polyethylene Vacuum 23-1 polypropyleneterephthalate surface Ex. 2,300,000 48,936 EVA on Polybutylene Vacuum23-2 polypropylene terephthalate surface Ex. 2,300,000 48,936 EVA onPolyethylene Vacuum 23-3 polypropylene naphthalate surface Ex. 2,300,00048,936 EVA on Oriented Vacuum 23-4 polypropylene polypropylene surfaceEx. 2,300,000 48,936 EVA on Oriented Vacuum 23-5 polypropylenepolyethylene surface (EVA: ethylene-vinyl acetate copolymer) EVA oradhesive is disposed only at a portion opposite the flexible coveringmember surface.

TABLE 5 Usable or not without damage Damage of battery casing after 1.5m and pack after 10 m drop drop test test Example 1-1 OK Battery casing:No damage Battery pack: Unusable Example 1-2 OK Battery casing: Nodamage Battery pack: Unusable Example 1-3 OK Battery casing: No damageBattery pack: Unusable Example 1-4 OK Battery casing: No damage Batterypack: Unusable Example 1-5 OK Battery casing: No damage Battery pack:Unusable Example 1-6 OK Battery casing: No damage Battery pack: UnusableExample 1-7 OK Battery casing: No damage Battery pack: Unusable Example2-1 OK Battery casing: No damage Battery pack: Unusable Example 2-2 OKBattery casing: No damage Battery pack: Unusable Example 2-3 OK Batterycasing: No damage Battery pack: Unusable Example 2-4 OK Battery casing:No damage Battery pack: Unusable Example 2-5 OK Battery casing: Nodamage Battery pack: Unusable Example 2-6 OK Battery casing: No damageBattery pack: Unusable Example 2-7 OK Battery casing: No damage Batterypack: Unusable Example 3 OK Battery casing: No damage Battery pack:Unusable Example 4 OK Battery casing: No damage Battery pack: UnusableExample 5-1 OK Battery casing: No damage Battery pack: Unusable Example5-2 OK Battery casing: No damage Battery pack: Unusable Example 5-3 OKBattery casing: No damage Battery pack: Unusable Example 5-4 OK Batterycasing: No damage Battery pack: Unusable Example 5-5 OK Battery casing:No damage Battery pack: Unusable Example 5-6 OK Battery casing: Nodamage Battery pack: Unusable Example 5-7 OK Battery casing: No damageBattery pack: Unusable Example 5-8 OK Battery casing: No damage Batterypack: Unusable Example 5-9 OK Battery casing: No damage Battery pack:Unusable Example 5- OK Battery casing: No damage 10 Battery pack:Unusable Example 5- OK Battery casing: No damage 11 Battery pack:Unusable Example 5- OK Battery casing: No damage 12 Battery pack:Unusable Example 6-1 OK Battery casing: No damage Battery pack: UnusableExample 6-2 OK Battery casing: No damage Battery pack: Unusable Example6-3 OK Battery casing: No damage Battery pack: Unusable Example 6-4 OKBattery casing: No damage Battery pack: Unusable Example 6-5 OK Batterycasing: No damage Battery pack: Unusable Comparative Unusable due toBattery casing: No damage Example 1 deformation Battery pack: UnusableComparative OK Battery casing: Damaged Example 2 Battery pack: UsableComparative OK Battery casing: Damaged Example 3 Battery pack: UsableComparative Unusable due to Battery casing: Damaged Example 4deformation Battery pack: Usable

TABLE 6 Usable or not without damage Damage of battery casing after 1.5m drop and pack after 10 m drop test test Example 7-1 OK Battery casing:No damage Battery pack: Unusable Example 7-2 OK Battery casing: Nodamage Battery pack: Unusable Example 7-3 OK Battery casing: No damageBattery pack: Unusable Example 7-4 OK Battery casing: No damage Batterypack: Unusable Example 7-5 OK Battery casing: No damage Battery pack:Unusable Example 7-6 OK Battery casing: No damage Battery pack: UnusableExample 8-1 OK Battery casing: No damage Battery pack: Unusable Example8-2 OK Battery casing: No damage Battery pack: Unusable Example 8-3 OKBattery casing: No damage Battery pack: Unusable Example 8-4 OK Batterycasing: No damage Battery pack: Unusable Example 8-5 OK Battery casing:No damage Battery pack: Unusable Example 8-6 OK Battery casing: Nodamage Battery pack: Unusable Example 8-7 OK Battery casing: No damageBattery pack: Unusable Example 9 OK Battery casing: No damage Batterypack: Unusable Example 10-1 OK Battery casing: No damage Battery pack:Unusable Example 10-2 OK Battery casing: No damage Battery pack:Unusable Example 10-3 OK Battery casing: No damage Battery pack:Unusable Example 10-4 OK Battery casing: No damage Battery pack:Unusable Example 10-5 OK Battery casing: No damage Battery pack:Unusable Example 10-6 OK Battery casing: No damage Battery pack:Unusable Example 10-7 OK Battery casing: No damage Battery pack:Unusable Example 10-8 OK Battery casing: No damage Battery pack:Unusable Example 10-9 OK Battery casing: No damage Battery pack:Unusable Example 10- OK Battery casing: No damage 10 Battery pack:Unusable Example 10- OK Battery casing: No damage 11 Battery pack:Unusable Example 10- OK Battery casing: No damage 12 Battery pack:Unusable Example 11-1 OK Battery casing: No damage Battery pack:Unusable Example 11-2 OK Battery casing: No damage Battery pack:Unusable Example 11-3 OK Battery casing: No damage Battery pack:Unusable Example 11-4 OK Battery casing: No damage Battery pack:Unusable Example 11-5 OK Battery casing: No damage Battery pack:Unusable

TABLE 7 Usable or not without damage Damage of battery casing after 1.5m drop and pack after 10 m drop test test Example 12-1 OK Batterycasing: No damage Battery pack: Unusable Example 12-2 OK Battery casing:No damage Battery pack: Unusable Example 12-3 OK Battery casing: Nodamage Battery pack: Unusable Example 12-4 OK Battery casing: No damageBattery pack: Unusable Example 12-5 OK Battery casing: No damage Batterypack: Unusable Example 12-6 OK Battery casing: No damage Battery pack:Unusable Example 12-7 OK Battery casing: No damage Battery pack:Unusable Example 13-1 OK Battery casing: No damage Battery pack:Unusable Example 13-2 OK Battery casing: No damage Battery pack:Unusable Example 13-3 OK Battery casing: No damage Battery pack:Unusable Example 13-4 OK Battery casing: No damage Battery pack:Unusable Example 13-5 OK Battery casing: No damage Battery pack:Unusable Example 13-6 OK Battery casing: No damage Battery pack:Unusable Example 13-7 OK Battery casing: No damage Battery pack:Unusable Example 14 OK Battery casing: No damage Battery pack: UnusableExample 15 OK Battery casing: No damage Battery pack: Unusable Example16-1 OK Battery casing: No damage Battery pack: Unusable Example 16-2 OKBattery casing: No damage Battery pack: Unusable Example 16-3 OK Batterycasing: No damage Battery pack: Unusable Example 16-4 OK Battery casing:No damage Battery pack: Unusable Example 16-5 OK Battery casing: Nodamage Battery pack: Unusable Example 16-6 OK Battery casing: No damageBattery pack: Unusable Example 16-7 OK Battery casing: No damage Batterypack: Unusable Example 16-8 OK Battery casing: No damage Battery pack:Unusable Example 16-9 OK Battery casing: No damage Battery pack:Unusable Example 16- OK Battery casing: No damage 10 Battery pack:Unusable Example 16- OK Battery casing: No damage 11 Battery pack:Unusable Example 16- OK Battery casing: No damage 12 Battery pack:Unusable Example 17-1 OK Battery casing: No damage Battery pack:Unusable Example 17-2 OK Battery casing: No damage Battery pack:Unusable Example 17-3 OK Battery casing: No damage Battery pack:Unusable Example 17-4 OK Battery casing: No damage Battery pack:Unusable Example 17-5 OK Battery casing: No damage Battery pack:Unusable

TABLE 8 Usable or not without damage Damage of battery casing after 1.5m drop and pack after 10 m drop test test Example 18-1 OK Batterycasing: No damage Battery pack: Unusable Example 18-2 OK Battery casing:No damage Battery pack: Unusable Example 18-3 OK Battery casing: Nodamage Battery pack: Unusable Example 18-4 OK Battery casing: No damageBattery pack: Unusable Example 18-5 OK Battery casing: No damage Batterypack: Unusable Example 18-6 OK Battery casing: No damage Battery pack:Unusable Example 18-7 OK Battery casing: No damage Battery pack:Unusable Example 19-1 OK Battery casing: No damage Battery pack:Unusable Example 19-2 OK Battery casing: No damage Battery pack:Unusable Example 19-3 OK Battery casing: No damage Battery pack:Unusable Example 19-4 OK Battery casing: No damage Battery pack:Unusable Example 19-5 OK Battery casing: No damage Battery pack:Unusable Example 19-6 OK Battery casing: No damage Battery pack:Unusable Example 19-7 OK Battery casing: No damage Battery pack:Unusable Example 20 OK Battery casing: No damage Battery pack: UnusableExample 21 OK Battery casing: No damage Battery pack: Unusable Example22-1 OK Battery casing: No damage Battery pack: Unusable Example 22-2 OKBattery casing: No damage Battery pack: Unusable Example 22-3 OK Batterycasing: No damage Battery pack: Unusable Example 22-4 OK Battery casing:No damage Battery pack: Unusable Example 22-5 OK Battery casing: Nodamage Battery pack: Unusable Example 22-6 OK Battery casing: No damageBattery pack: Unusable Example 22-7 OK Battery casing: No damage Batterypack: Unusable Example 22-8 OK Battery casing: No damage Battery pack:Unusable Example 22-9 OK Battery casing: No damage Battery pack:Unusable Example 22- OK Battery casing: No damage 10 Battery pack:Unusable Example 22- OK Battery casing: No damage 11 Battery pack:Unusable Example 22- OK Battery casing: No damage 12 Battery pack:Unusable Example 23-1 OK Battery casing: No damage Battery pack:Unusable Example 23-2 OK Battery casing: No damage Battery pack:Unusable Example 23-3 OK Battery casing: No damage Battery pack:Unusable Example 23-4 OK Battery casing: No damage Battery pack:Unusable Example 23-5 OK Battery casing: No damage Battery pack:Unusable

Brief descriptions of the structures and properties of the battery packsin the Examples and Comparative Examples shown in Tables 1 to 4 are madebelow.

In the group of Examples 1, different materials are individually used inthe outer covering layer of the rigid covering member. In the group ofExamples 2, the material for the metal layer of the rigid coveringmember in Example 1-1 is changed to different materials. In Example 3,the thickness of the outer covering layer of the rigid covering memberin Example 1-6 is increased. In Example 4, the material for the metallayer of the rigid covering member in Example 3 is changed to stainlesssteel and the thickness thereof is increased. In the group of Examples5, the material for the bonding layer of the rigid covering member inExample 1-1 is changed to different materials. In the group of Examples6, the material for the outer covering layer of the flexible coveringmember in Example 1-1 is changed to different materials (see Table 1).

By contrast, in Comparative Example 1, the adhesive strength is lowerthan atmospheric pressure. A small impact/shock made the battery packimpossible to be fitted into an electric device (see Table 5).

In Comparative Example 2, the peel strength is higher than a breakingstrength of the flexible covering member. After the 10 m drop test, thebattery pack was able to be fitted into an electric device, but theflexible covering member was stretched and damaged, and the battery packexpanded in the electric device a few days later (see Table 5).

In Comparative Example 3, the battery is fixed to a conventional moldedcase with an adhesive double-faced tape, and the peel strength is higherthan a breaking strength of the flexible covering member. After the 10meters drop test, the battery pack was able to be fitted into anelectric device, but the flexible covering member was stretched anddamaged, and the battery pack expanded in the electric device a few dayslater (see Table 5).

In Comparative Example 4, the battery element is sealed withoutconducting deaeration in the flexible covering member. The adhesionbetween the battery element and the flexible covering member wasunsatisfactory, and the battery element was unsatisfactorily unifiedwith the flexible covering member. In 1.5 meters drop test, the batterypack was deformed due to lack of strength, and was unable to be fittedinto an electric device. Further, in the 10 m drop test, both thebattery element and the casing material were damaged, causing heatgeneration or gas generation (see Table 5).

In the group of Examples 7, different materials are individually used inthe outer covering layer of the rigid covering member to form acomposite layer. In the group of Examples 8, the metal layer of therigid covering member and the metal layer of the flexible coveringmember in Example 7-1 are individually changed to different materials ofthe same type each having a predetermined thickness. In the group ofExamples 9, the thickness of the metal layer of the rigid coveringmember in Example 7-1 is changed to 300 μm so that the total thicknessof the metal layers is 335 μm. In the group of Examples 10, thematerials for the composite layer and adhesive tape in Example 7-1 arechanged to different materials. In the group of Example 11, the materialfor the outer covering layer of the flexible covering member in Example7-1 is changed to different materials (see Table 2).

In Table 3, in the group of Examples 12, different materials areindividually used in the outer covering layer of the rigid coveringmember. In the group of Examples 13, the material for the metal layer ofthe rigid covering member in Example 12-1 is changed to differentmaterials. In Example 14, the thickness of the outer covering layer ofthe rigid covering member in Example 12-6 is increased. In Example 15,the thickness of the metal layer of the rigid covering member in Example14 is increased. In the group of Examples 16, the material for theadhesive tape in Example 12-1 is changed to different materials. In thegroup of Examples 17, the material for the outer covering layer of theflexible covering member in Example 12-1 is changed to differentmaterials.

In Table 4, in the group of Examples 18, different materials areindividually used in the outer covering layer of the rigid coveringmember. In the group of Examples 19, the material for the metal layer ofthe rigid covering member in Example 18-1 is changed to differentmaterials. In Example 20, the thickness of the outer covering layer ofthe rigid covering member in Example 18-6 is increased. In Example 21,the thickness of the metal layer of the rigid covering member in Example20 is increased. In the group of Examples 22, the material for thebonding layer of the rigid covering member in Example 18-1 is changed todifferent materials. In the group of Examples 23, the material for theouter covering layer of the flexible covering member in Example 18-1 ischanged to different materials.

As can be seen from Tables 5 to 8, with respect to each of the batterypacks in the Examples, after the 1.5 meters drop test, all the battery,battery casing, and battery pack can be used without any problems.

Further, with respect to each of the battery packs in the Examples,after the 10 meters drop test, the casing for battery pack was deformedand unable to be used, but the battery body and casing were not damagedand a phenomenon of gas generation or the like did not occur.

According to embodiment, by appropriately controlling the state ofbonding between the flexible covering member and the rigid coveringmember so that the adhesive strength and peel strength are in therespective predetermined ranges, there can be provided a battery packwhich is advantageous not only in that the load concentration on theflexible covering member is reduced and hence the battery pack isimproved in reliability or safety after suffering drop and has suchstrength that the battery pack can resist deformation or the like whenit suffers an impact/shock of short drop and, when the battery packsuffers an impact/shock such that the flexible covering member isdamaged, the appearance of the resultant battery pack advantageouslyreveals that the battery pack cannot be subsequently fitted into anelectronic device or charged, but also in that the battery pack has suchexcellent volume efficiency that the volume of the battery element to becontained can be as large as possible.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A battery pack comprising: a non-aqueous electrolyte secondarybattery including: a battery element including a positive electrode, anegative electrode, and a separator which are spirally wound or stacked,the separator being disposed between the positive electrode and thenegative electrode, the battery element including a non-aqueouselectrolyte composition, and a flexible covering member, formed of afirst laminated film, which covers the battery element, the firstlaminated film being composed of a first heat-bonding layer, a firstmetal layer, and a first outer covering layer which are laminatedsuccessively, wherein the flexible covering member is sealed alongaround the battery element while leaving electrode terminals of thepositive and negative electrodes extended out side the battery element;a rigid covering member which covers the non-aqueous electrolytesecondary battery together with the flexible covering member, the rigidcovering member being formed of a second laminated film composed of asecond heat-bonding layer, a second metal layer, and a second outercovering layer which are laminated successively; and a protectioncircuit board, housed in the rigid covering member, for controlling avoltage and a current of the non-aqueous electrolyte secondary battery,wherein the battery element and the flexible covering member adhere toeach other, and the flexible covering member and the rigid coveringmember are bonded with a adhesive strength equal to or higher thanatmospheric pressure and with a peel strength equal to or lower than abreaking strength of the flexible covering member.
 2. A battery packcomprising: a non-aqueous electrolyte secondary battery including: abattery element including a positive electrode, a negative electrode,and a separator which are spirally wound or stacked, the separator beingdisposed between the positive electrode and the negative electrode, thebattery element including a non-aqueous electrolyte composition, aflexible covering member, formed of a first laminated film, which coversa principal portion of the battery element, the first laminated filmbeing composed of a first heat-bonding layer, a first metal layer, and afirst outer covering layer which are laminated successively a rigidcovering member, formed of a second laminated film, which covers aremaining portion of the battery element and the flexible coveringmember, the second laminated film being composed of a secondheat-bonding layer, a second metal layer, and a second outer coveringlayer which are laminated successively, wherein the flexible coveringmember and the rigid covering member are bonded along around the batteryelement to seal the battery element while leaving electrode terminals ofthe positive and negative electrodes extended outside the batteryelement; and a protection circuit board, housed in the rigid coveringmember, for controlling a voltage and a current of the non-aqueouselectrolyte secondary battery, wherein the battery element and theflexible covering member adhere to each other, wherein the flexiblecovering member and the rigid covering member other than around thebattery element are bonded, with a adhesive strength equal to or higherthan atmospheric pressure and with a peel strength equal to or lowerthan a breaking strength of the flexible covering member.
 3. The batterypack according to claim 1, wherein the adhesive strength is 0.1 MPa ormore and the peel strength is 5.0 N/mm or less. The battery packaccording to claim 1, wherein: the rigid covering member and theflexible covering member are thermally fused, and the secondheat-bonding layer is composed of at least one resin selected from thegroup consisting of an ethylene-vinyl acetate copolymer, anethylene-acrylic acid copolymer, an ethyl acrylate copolymer, a methylacrylate copolymer, a methacrylic acid copolymer, a methyl methacrylatecopolymer, polyacrylonitrile, an ethylene-vinyl alcohol resin, apolyamide resin, a polyester resin, acid-modified polypropylene, and anionomer.
 5. The battery pack according to claim 1, wherein the firstheat-bonding layer is composed of cast polypropylene and/or castpolyethylene.
 6. The battery pack according to claim 1, wherein thefirst outer covering layer has a thermal conductivity of 1 or less and amelting temperature higher than that of the second heat-bonding layer.7. The battery pack according to claim 1, wherein the first outercovering layer is composed of a material which is different from that ofthe second heat-bonding layer, and which includes solely or acombination of at least one oriented resin material selected from thegroup consisting of polyolefin, polyamide, polyimide, and polyester. 8.The battery pack according to claim 1, wherein a laminated layer of thesecond outer covering layer and the second metal layer has a thermalconductivity of 1,000 Wm⁻²K⁻¹ or more per area.
 9. The battery packaccording to claim 1, wherein the rigid covering member is formed of acombination of the second metal layer having a thermal conductivity of50,000 Wm⁻²K⁻¹ or more per area and the second outer covering layerhaving a thermal conductivity of 1,050 Wm⁻²K⁻¹ or more per area.
 10. Thebattery pack according to claim 1, wherein the second metal layer iscomposed of at least one metal selected from the group consisting ofaluminum, copper, iron, stainless steel, and nickel or iron plated withat least one metal selected from the group consisting of tin, zinc, andnickel, and has a thickness of 330 μm or less.
 11. The battery packaccording to claim 1, wherein the second outer covering layer iscomposed of polyamide, polyester, or polyolefin and has a thickness of115 μm or less.
 12. The battery pack according to claim 11, wherein thepolyamide is oriented nylon 6, the polyester is at least one resinselected from the group consisting of polybutylene terephthalate,polyethylene terephthalate, and polyethylene naphthalate, and thepolyolefin is oriented polypropylene or oriented polyethylene.